The first rule of revolver (or any gun, really) buying in my book is "Buy the Gun, not the model." I mean that I want a better built gun regardless of which variant it is - if it's newer with less desirable features but tight, smooth, and well built, that will trump an aged classic with a loose action, Bubba trigger job, or some machining or fitting defect.
The 25-2 (old style) is a very good gun, but there were periods of less-than ideal quality control at S&W, I find it generally runs from '68 to '79. Guns in this (the Bangor-Punta management days) range I examine the same as any other in person, but I am more leery of when buying unhandled over the internet or by phone.
Apples to apples, I think the older gun is a much better deal. I think that price range should be able to find you an excellent older 25, so I'd go that route. But follow the "check out" steps stickied here. Try to get one with original grips - the lack of them should detract from the price. I am not against the "new" ones, and indeed, the few I have handled have been very well built, and I am hovering around buying a model 21 that is now being closed-out at a very good price. The only real problem I've seen with the new ones is inconsistent grip fit, which I find very annoying and disappointing. The old ones were all individually hand fit; the new ones are slapped on and even CNC production methods can't get it right every time.
Good luck. I have an N-frame .45LC (not a 25, though) and it is a hoot. Coincidentally, I was actually planning on taking it out this weekend for the first time in a year.