He's probably a better 5k guy, but making a 5k team now means finishing top 3 in a field with a 12:46, 12:51, and 12:54 guy (and maybe Nuguse too who can probably run in the 1240s). So he needs a 12:50 PR with kick to have good chances.
In the 1500m he's been a clear cut top 3 the last couple of years. Some more guys are coming up, but it seems like it would be easier for him to make the 1500m team.
Still, I think he should be going for the 5k. If he can make the team, he's a medal contender, capable of racing against 12:50 and below guys and utilizing his kick which is solid for the 5k. In the 1500m he perhaps makes more teams but has less of a shot at medals.
But then there is the final factor, the 1500m is a more prestigious event, so maybe he runs it even if it isn't his best event because he can make more money running 1500m races.
I don't know enough about him to know if he can steeple, but I think we'll be seeing some fast steeplers coming up now that it takes a low 12:50 PR to be a contender for the 5000m team. Few likely remember that a year or so before Solinsky's breakout season, there was a lot of talk of him moving to the steeple. I've always been curious how that would have worked out.