125 is cheaper to maintain, 250f is easier to trail ride, I ride my 125 on the trails with no issues, just shift more. If you don't like that try getting (based on your pic) a stock YZ pipe and see if that brings the powerband down a tad. After market pipes, fmf and procircuit pipes tend to give the bike more power through a more free flowing exhaust. This is great for mx or someone who can really rip the bike through the woods. However, the average rider needs the powerband lower in the RPM's so they have more usable power. I tried dual stage reeds and a reed spacer on my bike, I love the dual stage reeds, I really do not like the reed spacer, It made my bike really difficult to tune properly, but you have a completely different bike and your experience will vary. Another good option that is easy to add on is a flywheel weight. This takes no power from the bike, but will make the engine chug better and make it more difficult to stall. On a 125 i recommend the smallest FWW possible if thats the route you are going, there isn't enough rotating mass in the engine to dignify a 12oz+ FWW.