Google Ads, SEO, or email: how to compare marketing channels honestly

Three structural differences make the raw percentages incompatible, and none of them is obvious from a report.

The first is the denominator. Paid search ROI divides by media spend, which is most of the true cost. Email ROI divides by a platform subscription, which is a fraction of the true cost — the rest is your time, and it never appears. A 400% email ROI and a 40% paid search ROI can represent the same amount of profit, with email requiring far more unpaid labour.

The second is timing. A paid search click and its sale usually fall in the same month. An SEO retainer paid in January may produce nothing until May. Comparing a channel measured in-period against one measured out-of-period will systematically favour the fast one, regardless of which is the better investment.

The third is what happens when you stop. Turn off paid search and traffic ends that afternoon. Stop an SEO retainer and rankings persist for some time before decaying. Stop emailing and the list is still there. The channels differ in how much of what you bought you keep.

Four adjustments make the comparison defensible. None of them requires software you do not have.

First, use gross profit rather than revenue everywhere. This is the single largest source of misleading channel comparisons. A channel returning 2x on revenue at a 40% margin is losing money; the same 2x at an 80% margin is comfortably profitable. All three calculators on this site use gross profit for exactly this reason.

Second, count total cost, not just the invoice. For paid search that means media plus management fees plus creative plus landing pages. For SEO, the retainer plus internal review and approval time. For email, the platform plus a realistic value for the hours spent writing. Put your own time in at a rate you would actually pay someone else.

Third, use a consistent measurement window that is long enough for the slowest channel. Comparing over three months will make SEO look like a failure; comparing over twelve gives each channel time to show what it does. If you cannot wait twelve months, at minimum acknowledge that you are comparing a mature paid campaign against an immature organic one.

Fourth, separate branded traffic. People searching for your business name would mostly have found you anyway. Counting them as SEO performance — or worse, paying for them in paid search and counting them as campaign performance — inflates results in a way that survives no scrutiny.

Take a service business with a 55% gross margin considering where to put $2,500 a month. The figures below are illustrative, chosen to show how the method works rather than to predict what any channel will do.

Paid search at $2,500 of media, $12 per click, 8% landing conversion, 40% close, and $450 average sale returns roughly $1,980 of gross profit — a loss on media alone before the management fee. Its virtue is that you knew this within a month.

SEO at a $2,200 retainer, at the traffic the site has today rather than the traffic promised, might produce two or three clients. At 400 organic visits, 1.8% conversion and a 30% close rate that is around $1,400 of net return — modest, but the rankings that produced it do not switch off when the invoice does.

Email at a $95 platform bill against a 3,200-person list might return around $350 a month of gross profit. As a percentage that is the best of the three by a wide margin. In absolute terms it is the smallest number on the page, and it costs six hours of writing.

The honest conclusion is not 'email wins'. It is that paid search is currently losing money and can be diagnosed immediately, SEO is unprovable in-period but retains value, and email is efficient but capped by list size. Those are three different problems, and only one of them is a budget decision.

Once the numbers are comparable, the more useful question is what each channel does structurally — because that determines which problem it can solve.

Paid search buys immediacy and certainty. You can be visible this afternoon, and within a month you will know whether the economics work. It is the right choice when you need demand now, when you are testing whether a market exists, or when seasonality gives you a narrow window. It is the wrong choice as a permanent foundation, because you rent the traffic and the rent rises.

SEO buys durability. The work compounds and does not stop the day you stop paying. It is the right choice when you can survive two or three quarters without a return and when your customers genuinely search for what you do. It is the wrong choice when you need revenue this quarter, or when the total search volume for your service is too small to matter.

Email buys margin. It is the cheapest way to reach people who already trust you, and it converts at rates cold channels cannot approach. It is the right choice almost always — but it is capped by list size, which is why it works best alongside a channel that brings new people in. Email cannot grow a business on its own; it makes everything else more profitable.

Read that way, the three are not really competitors. Paid search and SEO both acquire; email retains. The common small-business mistake is running the two acquisition channels against each other while neglecting the retention channel that would improve the economics of both.

A practical order of operations, when you have limited attention rather than limited budget.

Start with conversion, not channels. Every channel multiplies by the same landing page and the same close rate. Improving the rate at which visitors become enquiries raises the return on all three simultaneously, and it usually costs nothing but attention. Doubling conversion has exactly the same effect as doubling traffic, and is generally cheaper.

Then fix the channel that is actively losing money. A negative paid search campaign is a bleeding wound; SEO that has not yet delivered is merely an unproven investment. Stop the bleeding first.

Then build the retention layer, because it improves the economics of whatever acquisition you do next.

Only then decide where new money goes. By this point you will have measured conversion, removed a loss, and improved margin — and the allocation question will be much easier to answer than it was at the start.

Every comparison above assumes you can attribute customers to a source. Most small businesses cannot, and the resulting figures are confident and wrong.

The three most common failures are broken or missing conversion tracking, counting form fills that are actually spam or recruitment enquiries, and attributing to a channel a customer who found you elsewhere and then searched your name. All three inflate results, and all three are common enough that a plausible-looking report should not be trusted without checking.

The lowest-effort fix that works: ask every new enquiry how they found you, write the answer down, and review it monthly. It is imprecise, people misremember, and it is still more reliable than an untested analytics setup. Run it for a quarter before making a significant reallocation decision.

If a channel cannot be measured at all, that is itself information. An unmeasurable channel should get a small, capped, deliberately-risked allocation — not a large one justified by faith.