So you want a big build volume, able to handle lots of filament, auto bed leveling and reliable/easy to work on.
Do you want big XY or big Z or both? The filament part is a bit vague as filaments are difficult to print for lots of different reasons that are dependent on different parts of the printer. Flexibles are mostly dependent on the extruder which is the easiest part of the hardware to modify in my opinion. Other than that the only thing that really affects it is the choice of bowden vs direct, where bowden makes things noticeably harder. Nylons are more temperature dependent which is to do with your enclosure (if any) and heated bed.
Auto bed leveling is available on most mid/high end printers (and even dirt cheap ones).

If I'm being honest, you'll likely get the same resolution out of any printer you buy. Most of them use the same T8*8 lead screw and the same 1.8 degree motors. You might get some difference if they happen to use 0.9 degree motors but that's about it.

The last one about being reliable and easy to work on is another tricky one. Just about any printer can become reliable depending on how much time you're willing to sink on it, even the cheap chinese ones. As far as easy to work on, the prusa type and lulzbot printers rank high. The prusa is popular and there are lots of upgrades, mods and information out there while lulzbot provide excellent documentation and use lots of printed parts so you can change or modify lots about the printer. The only lulzbot in your price range has a 150mm ish cube buid volume though, and prusas have an average build volume. I'm not the biggest fan of either as they use a mendel motion system, though.