With the development of TaiHENkaku lately, it's ill advised to stay on a lower firmware.
Not only can you benefit from Vita games, you can also install Adrenaline (you'll have to use a PSP mini or PSP Demo or PSP game) which is kinda like TN-X (the PSP XMB on Vita one) and around February/March, you'l be able to enjoy PS1 games on it as well.
Not to mention that emulators in Vita mode run a lot better then in PSP mode.