having had a 17hp kubota and moved to a 35hp kioti I can tell you there is a WORLD of difference when you double the HP/weight.
HP makes things go 'quicker' and you may need if for 'real' farm work (plowing big acres, haying, etc). Hence these 25-60 hp tractors are called 'utility' tractors. Odd jobs sorta thing.
Bigger costs more to buy, to run, BUT can handle bigger implements (which also cost mroe) but can get the work done faster, easier and maybe safer (on hills, less tendency to overload them).
For mowing you can get a rear mower for any of them, or for 3k ish get a new zero turn (the cost of a deck on a kubota is 3kish). Taking a mid deck on/off sucks.
As for DPF - if there's no DEF fluid then it should be a non-issue -just keep revs above 1800 to keep the exhaust hot and particulates low and go for it. It's lots of low rpm, start/stop, idling that causes the filters to 'get used' more and therefore regen more.
I went with 35hp over 25 hp (same frame on the kioti) was heavier duty/capable loader and the HP to run a 1' bigger brush hog (main task). I may hay in the future and 30 hp pto can do it -it's at the low end but i'm gonna hay 10 acres, not 100. Also, working a bigger tractor less hard should help it last longer.