Barry
My 26 was fitted with a Beta 14 when I purchased, now approaching 20 years old with about 1,100 hours running. I would strongly recommend the make, it has never missed a beat and apart from an upgrade on the drive belt and a replacement ignition switch (ordered by phone at 3.00pm Friday, delivered 1st post the next morning) has required nothing more than routine maintenance.
The 25 would appear the one, only 3kg more than the 3YM20 and much less then the 3TM30. The 30 is another 26kg more than the 25, seems a lot.
Philip
rascal