Someone just starting, should they use GitHub? Gitlab? Something else?

The truth of the matter is that if you're just starting out, it doesn't really matter. For basic coding needs, they both pretty much do the same thing. If your needs mature, you'll start to see minor differences that may or may not matter to you (pricing, team management, SEO, etc.).

If you're looking for a single reason, here's one... look at the aesthetics for GitHub & GitLab. Decide which one you like more and use that. When you start to feel like something is missing or suboptimal from the service you chose, give the other one a try!

Don’t use any of this go with fossil-scm [1] or sr.ht [2] both are solid choices. You can pick either depending the kind of workflow you like. Especially with respect to fossil it’s a very clean and beautiful and highly performant even compared to git with everything self contained in one binary.

[1] https://fossil-scm.org/home/doc/trunk/www/index.wiki

[2] https://sr.ht/

Github. It is the simplest thing that might work. It is the most well documented option. It is the ordinary choice.

The reasons to use something else:

1. You are already using something else.

2. An ideological agenda that is more important than learning Git (there's nothing wrong with that, problems are in not acknowledging it).

3. An unusual set of circumstances that make Github unusually difficult to use. E.g. the Great Firewall.

4. Architectural design such as not taking dependencies on external services.

Otherwise, it's probably can-becoming-must contrarianism.

IMHO, it makes no difference. The more important point is to consider the reasons for having a (1) public repo and (2) hosted by a third party in the first place.

Pick the one which hosts more projects you may want to contribute to. It will incentive use of the platform, thus learning it faster.

If you don’t know which of those it is, defaulting to GitHub might be the safer bet.

Of course, this is only a single data point ...

I would pick GitHub, simply because it hosts most of the projects that I already use in some form.

GitHub communities for most projects are very supportive and engaged.