Jea,
I went with the 4310 after hearing tanuke01's <A target="_blank" HREF=http://www.tractorbynet.com/cgi-bin/compact/showthreaded.pl?Cat=&Board=buyjd&Number=55211&Search=true&Forum=All_Forums&Words=tanuke01&Match=Username&Searchpage=0&Limit=25&Old=allposts&Main=55056> frustrations </A> with the 4200. I needed the JD front mounted 59" snowblower and it seemed the 4200 was underpowered for the task.
When I sat down at looked at the implement specs and what you could put on a 4200/4210 vs. a 4300/4310, the choice became crystal clear for me. I ordered the 430 loader, 48 backhoe and 59" snowblower.
Had I gotten a 4200/4210, I would only have the option of the 47 backhoe, been stuck with the same snowthrower and less than adequate power and a lesser loader. I really didn't want to spend the extra $$$, but it gave me choice of implements I didn't have with the 4200/4210. Simply put, the 4300/4310 gives you better performance and more choice. From a performance/price curve, it is no wonder the 4300/4310 is the top selling model in the series.
These choices are always difficult and all too frequently dictated by one's available funds. In the end, I think you would be happier with more choice and performance. The 4200/4210 has the same "footprint" more or less as the 4300/4310, so if you have tight spaces the 4200/4210 isn't going to help any and the 4300/4310 isn't going to hurt.
One last thing, if you're like me you probably aren't considering resale value because this tractor is going to last a lifetime, but.... If you ever wanted to trade up or fell on bad times, the 4300/4310 with the better performance and greater popularity would in my opinion sell faster and for more.
Not to slight any 4200/4210 owners (I seriously considered one), but I think that model is chosen primarily on a price basis, when one would need/want a 4300/4310, but cannot afford it. Other than price, I can't think of too many compelling reasons to buy it.
I believe the opposite is true for the 4400/4410, that is a tractor that offers nothing more with regard to implement choices and adds 3 horsepower for another $1,800. If those extra horsepower are worth that much, then by all means, get them, but once again, that choice is not compelling for most people.
Well, that's my $0.02. There are plenty of other opinions out there and mine is just one of them. I hope this helps bring a little more perspective to your situation. Good luck,
Sleepyhollow