>>50219673HGSS definitely improved the gameplay in a lot of ways. For the most part, the only differences are aesthetic, but I'm not really an artsy guy so I can't comment in-depth. I'll just say that I very much prefer the GBC look and music. I can say that HGSS are a bit more handhold-y in places, and I definitely think that a few of the changes are for the worse (I'm mostly thinking of the Ho-Oh/Lugia encounters, which are way more subdued and atmospheric in GSC). Those changes are few and far between, though, and overall HGSS are among the best in the series.
What I will recommend is playing the ROMhack Polished Crystal. It adds a ton of new content (most of it optional, so you can still have a pretty faithful experience if you want) and fixes the level curve. But none of the new areas clash with the atmosphere of the original game at all, which I find very impressive on the part of the dev.
