I'm a happy 1870 owner, and went that way mostly because the 48" deck is a better fit for lots of tight spaces and trails on my property. But if that model doesn't fit your needs, I'd be wary of trading up just to the 2370. On paper that's a nice jump in horsepower. But I'm not sure if you'll see that much of difference in actual use. If you need a more capable tractor, you might not be satisfied until you're in the B or L series, with 26 HP (or more) and more torque. If it were me, I'd try to arrange a trial, or even rent one of the bigger BXs to see if it meets the need.
You NAILED it. Id be real leery of trading a 1870 in on a 2370. MOST likely in a year of owning the 2370 you’ll be in the same boat, wishing youd of got an even bigger machine. I just went through this myself. Owned a 2370 and wanted a little bigger. Was gonna get a b2301, then thiught to go with the b2601, THEN finally came to my senses and just went with the b2650 and couldn’t be more happy!