Two different things get collected under the same heading, and a local service business that treats them as one thing tends to end up with neither.
A testimonial is a quote you asked for, trimmed for length, and placed on a page you own. You decide which ones appear, in what order, and whether a weak one appears at all. A Google review is a quote you did not collect, cannot edit and cannot take down, published on a profile you do not control, in the spot someone looks at before they decide whether to call you.
That difference is the whole comparison, and every practical question about the two follows from it.
The pages that rank for this are written for a different business
Search the term and you get testimonial page galleries, video testimonial services and collection widgets, aimed at software companies with a website funnel and a sales team. For a roofer, a clinic or a salon the funnel starts somewhere else: a map result with a star rating beside it. That advice is not wrong. It is written for a business whose first impression is its own homepage, and yours is not.
What each one actually does
A testimonial works on someone who has already arrived. They are on your page, half convinced, looking for a reason to stop worrying. A named quote about the exact job they are about to book is the right thing to hand them, and you can place it next to the service it describes.
A Google review works on someone who has not arrived yet and may never see your website at all. It sits under your business in Maps and in search, next to a count and a rating, in a set a stranger scrolls through while choosing which of three numbers to dial. You cannot curate it and you cannot order it. That is precisely why a stranger reads it.
So the two are not rivals. One gets you onto the shortlist. The other closes.
Asking for both in one message is how you get neither
Here is the part the collection guides skip. You get one clean ask per job, in the short window when the work is finished and the customer is pleased with you. Spend it on two requests and you have handed them a decision to make. A decision is where the reply rate goes.
Our post on asking customers for reviews argues for one ask, one link, no choices. That holds here too. Pick the asset that the next customer for that job will actually see, send that single request, and let the other one come later from a different direction.
For a business whose enquiries arrive through a map, that means the Google review. It is the one you cannot manufacture, and the one that decides whether you show up in the shortlist at all. A testimonial can be assembled afterwards out of a review that is already public, with the customer's permission and a link back to the original, which is both less work and more credible than a fresh ask.
Only one of them has rules attached
This is where the two genuinely diverge, so it is worth stating plainly. On your own site you choose which testimonials to publish and nobody would call that unfair. On Google, choosing is against the rules. Google's contribution policies list, under prohibited merchant behaviour, "Discourage or prohibit negative reviews, or selectively solicit positive reviews from customers." The same policies treat offering "payment, discounts, free goods and/or services" in exchange for a review as fake and misleading content, and Google's own guidance on getting reviews says the way to do it is to "ask customers to visit a Google link or scan a QR code."
So the instinct that builds a good testimonial page, keep the strong ones and quietly drop the rest, is the instinct that gets a Google profile into trouble when it is carried across. The review request goes to every customer, in the same words, whatever you expect them to say. That is not a compliance chore. It is the reason the rating means anything to the person reading it.
What to do with this
Send one request per finished job, to everybody, pointing at your Google review link. Review request templates has wording you can copy. Once the reviews arrive, good review examples shows what a useful one reads like, and the strongest of them are the raw material for a testimonial page: already written, already public, already signed by a real customer.
Build the testimonial page second, out of the reviews you already have.