This is akin to asking what the best ice cream flavour is -- everyone has their personal fav.
I use Mighty ROM 5 and it works great for me. I'm very happy with it. Others have tried it and moved to something else. YMMV. Thankfully it doesn't take long to flash so just try a few until you find one you like the best, then you can move on with customising it and setting it all up!
/Kevin