only advantage the KTM has over the Z250 or R25 would be the ABS...otherwise, they are quite known for electrical problems and also the RC has a rather racing seating position...which can get uncomfortable for long distance santai ride. the single piston engine for both KTMs also creates quite alot of vibrations which again can be uncomfortable for long rides. but of course, commfort, is down to the rider's capability of handling it.
my comments above are based on feedback of Duke 250 (weird, unsolvable intermittent check light issue) and RC250 (replaced entire burnt wiring harness before) riders in my group.
as mentioned, Z300 already comes with ABS. so thats an option. twin cylinder will have lesser vibrations. plus seating position is quite decent for long rides.
as for Z250 having lower top speed than R25, thats mainly due to the rev/speed cut. remove them (not recommended) and u can go further.. there are Z250s out there that touches 190km/h.
if ur more into sportbikes, r25 and ninja 250 has a less racing seating position which makes it ideal for daily commute and long rides due to less chances of back and wrist ache. Z250 has a slightly more upright seating position compared to these 2.
i myself am a Z250 rider... which i bought used at 44k km mileage 1.5 years ago. love the bike...really great performer and very reliable. this is my daily bike (66km-2way) and also my santai joy ride bike...my bike is now at 71k km mileage. love riding it so much that i racked up almost 30k in less than 2 years

in fact, i just came back from a 605km ride... havent even bathed yet hahahah.
shah alam - ipoh - simpang pulai - cameron - sungai koyan - bentong - karak - wangsa maju - shah alam.
EDIT: oh yeah, forgot to mention that if ur thinking of buying a 250cc bike, id recommend buying used. the itch to upgrade will come very quickly and the itch is very strong.... so if u do, at least u wont lose out much.
This post has been edited by mADmAN: Oct 26 2017, 11:30 PM