By all accounts, the 3300 is a solid AVR. If there are no added features of the 4300 that are of compelling value to you, save the $200!
You have probably seen it, but here is the review of the 3300.
Be wary of reading the power charts as AH put the power chart for a Yamaha AVR just before the Denon (to emphasize that the Yamaha was an uncharacteristically poor design)
http://www.audioholics.com/av-receiver-reviews/denon-avr-x3300w-1
But try to wait another day for responses, someone else may know a reason you want a feature that you don't believe you do.
What speakers will you be using?
Evaluate those uncertainties in bold, obviously, they are key to your decision.
For planning purposes, I'd look at an AVR as a 8-12 year purchase (unless something truly amazing is introduced and made price competitive before then).