I mostly run a 32" lighweight on the 500i...it does just fine on the softwoods around here. It even works pretty well on the oaks, as long as I don't lean on it too hard. If I really need it, I've got an 066 that I run either a 36" lightweight or a 42". The 066 does feel signifigantly stronger than the 500i, but I've ported the 066, custom exhaust, max flow, etc...while the 500i is bone stock other than exhaust.
At my real job, I run a 462 with a 28" lightweight. I went with the 462, as I need multi purpose saw. Sometimes cutting brush, sometimes falling weakened hazard trees. That saw and bar combo(or a 400/28") is the most versatile set up IMO.