I looked at new 4310s' for quite a while, just couldn't quite squeeze up enough justification to buy new. My list was the same as yours, 430 loader, E hydro, but with the R-4 tires and a 48 backhoe.
Best price I found was right at 26K.
Then I came across a used one, 3 months old with 24 hours, but, it had the 420 loader, Power Reverser, 47 backhoe, and the large 6 ply R-1 tires. Even came with a 16' steel bed trailer, chains, locks, saved about 6K buying this one.
The 420 loader works very well. it will accept the same attachments as the 430. It has done everything I have asked of it so far. That being said, I still stopped by the dealer last week and asked him to call me if he got a used rig in with a 430 on it. I would like to upgrade. The 430 has higher reach, picks up more weight, and is built a fair amount stronger overall.
If you are just doing lighter type work, the 420 will probably do all you need. But for $635.00 more, I would get the bigger loader. You'll get it back when/if you sell, and as a percentage of the total price, it really isn't that much.
Don't know where you live, but if your with in 500 miles of me, and want the 420 loader, go ahead and get the 430, I'll bring you my 420 (still in great shape) and $800.00 to trade.
Good luck with the new tractor,
DT