In general, on mobile, without heavy TDP (power/thermal) constraints, it looks like the 4800u should be roughly on par with the MX250 in most situations, maybe just a bit behind. I would expect that the 4700U should be able to keep up with the MX230. The 4600u/4500u seem to have taken a bit of a GPU performance regression from the 3500U in a few of the benchmarks that I've seen, though, again, its very limited.
Essentially, if you find a 4500/4600 with a dgpu that's less expensive than the 4700/4800u and have any intentions of doing low spec gaming, the 4500/4600 is the better buy. If you find the 4700/4800 cheaper, then unless the 4500/4600 has a substantially better dGPU, the 4700 is the better buy. I suspect that, for purely mobile gaming though, where you have to run just off the battery, the 4700/4800u will give you the best of all worlds if you balance performance, battery life, portability and cost. I think that, if people are willing to game at a rendering resolution of 720p and use RIS with upscaling to 1080p, the mobile experience should be just fine for most people.
I do wonder how good the 4800u can be? We haven't gotten a good round of benchmarks off of a system that's outfitted with "dual" channel LPDDR4X 4266 in a system with proper TDP up and cooling. I suspect that it'll get a good 5-10% higher results in that configuration...