I own one (a Kubota L3302) with a 33 HP engine, and there are a few guys around me who have 25 HP subcompacts (Kubota, Kioti, and JD) that do similar work to mine. It's astonishing how much everything around those 25hp tractors stinks of diesel. All the time. And how everything gets coated in a fine black greasy dust. I have very little of that.

I've read before that for the average homeowner, the particulate/NOx/CO emissions from their little 5 HP 4-stroke carbureted lawnmower and 40cc 2-stroke carbureted blower/stringtrimmer/etc are often greater than that of their 150 HP automobile - which has an ECU and oxygen sensors and fuel injectors and catalytic converters and so on.

The price bump to go up to the 33 HP engine with the emissions controls was significant (much more than the 8HP performance bump), and every 30 hours or so it wants to run a "regen" cycle which always seems to be at the worst possible moment in my workload, but I feel a lot less guilty about running it knowing that my exhaust isn't nearly as bad for the environment and for my lungs as it could be at a slightly lower performance tier.

I noticed this https://toolguyd.com/makita-xgt-motor-unit-launch/ and wonder if it's going to go anywhere - there are obvious advantages to "electric" but it's a hard sell to those already using existing equipment.