Time to answer my own topic! While I like both Pokemon, I've had better experience in using Lunatone, and I think it's design is a bit better. But I'm also a night person, so maybe that has to do with it. I do like that Solrock is a bit of a pseudo-Fire type though, and I think it's fun to use!
One thing I've always liked about the two is that the moon is related to water, and Lunatone is in Sapphire with Team Aqua as the bad guys. And the sun is, of course, related to fire and Solrock is in Ruby where Team Magma are the bad guys. Pretty neat touch when you think about it. Plus they did that without outright making their types Water/Rock and Fire/Rock, or something. One complaint I do have about Lunatone though is that it should be able to learn some sort of Water move. Other Rock types can have Surf, so the "but using something it's weak to" argument won't work lol. But like I said, the moon is related to water, and Solrock can use Fire moves. I thought it'd only be fair. But oh well.