Psychic, the L and R buttons are mainly used for convenient box-swapping in the PC screen. They're not integral to the games in any way (unless you think you'll need to soft reset often), but they make using the PC slightly easier. And SoulSilver will certainly be worth the buy. I'd recommend Platinum even more strongly, but that's largely just preference.
I hope you can swing it with the pink one, if you decide to! =)
I hope you can swing it with the pink one, if you decide to! =)