It really depends on you. If you are like 99% of us and love tweaking, adding on, getting 2% more power, etc. you don't want to have ended up buying a 590 and putting more $$$ into it to equate to a 620p. In other words, but the better one up front if you remotely want to tinker / improve your saws. Everything you read on comparing these models, says the cost difference is a no brainer in favor of the 620p.
I've only owned the 620p and the only time it had me wishing for more was big hardwoods 28"+. For firewood tasks if was excellent.