Seen as this is clearly an opinion thread i may as well put in my 10p
I started trials biking about two and a half years ago, i started with a gas gas 250 2010, then a gas gas 280 2012 racing (bought from katy sunter so it had all the little bits to make it softer flywheel weight carb spacer etc). Which both were fantastic bikes that really got me back into trials biking, the gas gas 2010 was amazing after i toned it down with a few mods.
Then in january of this year i purchased a montesa 4RT 2014, after spending some money on a few mods and getting the clutch abit softer, for a clubman rider ( as i'll never be anything but) the Montesa in my opinion is a brilliant bike, once you get used to the different power delivery it is quite an effortless bike to ride.
So for me its fuel injection 4 stroke all the way , they are both good in there own way depends how you ride....