There's compact and sub-compact; sub-compacts would be the BX and B series for Kubota. I don't know models for other tractors. Compacts would be the L series, LX series Kubota's. Like my L3901. As you said seems like the general cutoff is about the 40hp mark; as I would not classify the L4701 as a compact tractor though it still might be considered one.
I find the BX series to be not very usefull as a tractor; Maybe if all you need to do is load buckets of mulch or similar I can see that purcahse, but as a utility tractor it's a waste of money IMO. I don't think they're geared for that kind of thing either. There the Big B tractors like the 26hp that you can get some better numbers on for loader capacity but nothing with a pto hp to run anything more than a finish mower.
0% financing is going to be hard to beat anywhere. tractors and equipment are just going to keep going up in price in the next couple years; and they keep their value even without inflation. I know the B2301 is very popular. I would look at the LX2610 too personally; slightly smaller than the L2501, but bigger than the B series. Kind of like a Big B series tractor. Plus the LX2610 doesn't have the DPF system while still being tier 4 compliant. You can get a few more fancy options with the LX that you don't get in the L2501. Plus it still has the options for a belly mower.
Like I said, I went with the L3901 because I had a lot of ground engaging 3pt equipment that I needed the HP and PTO HP for, and the use was more utility than homeowner type work. I will say, that on every Kubota now, they all use a quick on/off system on their loaders that make it ridiculously easy and quick to take the whole loader off the tractor; not the swift-latch system (mentioned earlier I think)
I'll expand on this a bit, though I agree with most of it.
The B is definitely considered a compact, not a subcompact. It's just on the low end of the compact, similar to a Deere 2025R(which is essentially just a 1025R with bigger tires). They changed the B2650 and B3350 to LX2610 and LX3310 so people would stop being confused between "big B" and "small B".
I agree the BX is basically a 4WD lawnmower for people who want a loader and/or baby backhoe. They're way beefier than low end mowers like you'd find at big box stores, but they're still fairly light duty compared to compacts. But their capabilities are still pretty underrated by most. They'll do some serious work. Still not what I'd get if you have a separate dedicated lawnmower. If you're set on a subcompact, the Deere 1025R beats the Kubota BXs in pretty much every category.
The B2301 and B2601 are smaller than LX, but also more basic. Stuff like tilt steering, fancy seat, quick attach bucket, etc are all optional on those where they're standard on the slightly bigger LX. And they're all pretty handy features, most dealers outfit them with at least some of those items, which really narrows the price gap between them. But there can definitely be advantages to the slight smaller B depending on your usage. If you were to mow with it, the ground contact deck on the LX does a much nicer job than the floating deck on the B. My yard is very uneven and even with a wider deck my LX mows much nicer and less scalping than the my previous machine.
Agreed the standard loader is plenty quick enough to install and remove. Like 2-5 minutes of work depending how many beers you've had. The swift-tach is marginally faster, but way more problematic. People have had them come off and do serious damage, and there were several recalls on it just this year. It's a solution in search of a problem. Standard loader is fine, but quick-attach bucket is a must(SSQA) rather than pinned. Also get the biggest bucket available for that model, which is a 54" for the B, 60" for LX. They call the bigger one a "light material bucket". In reality the construction is identical, they just let the lawyers name it so people can't blame them if they overload it. I've filled mine with clay and gravel with zero problems.
Rear ballast is a must. I was going to fab something up, but ended up buying a ballast box with the tractor and filled it with an additional 500lb of concrete and scrap steel. It's a game changer for both lift capacity and safety. I recently moved a stack of empty pallets without rear ballast and even that was pucker factor in my hilly yard. Loaded tires are also a great option, only reason I haven't done that is to minimize lawn damage when mowing. Might still do it eventually.
Good point on PTO power for ground engaging implements. Not much of a consideration for my use, but definitely is for some people.
I'd buy the B2601 over the B2301. The extra $900 or whatever it is will be worth it for the power, and even more worth it for resale if you ever get rid of it. Always best to get the most power available in that chassis size....except with the LX IMO. Stepping up to the LX3310 was a $3k+ upgrade and adds a bunch of complexity and emissions crap I don't want to be dealing with in 20+ years. And I didn't need the PTO power.
Shitty part is right now you might have a hard time finding a dealer with multiple models in stock to sit on and evaluate. Lots of places are on backorder right now, but MI dealerships seem to be a bit better than others I've seen online.