This is the point…for a V2 to get as much power, and more importantly, torque, as an IL4, it needs the extra capacity of around 200cc. Thats why in Superbike class, the IL4s are 1000cc, whilst the V2s are 1200cc.
Horsepower = torque x revs therefore if you have two bikes with equal torque but one can rev to twice the other, it will produce more horsepower and therefore accelerate faster.
Thats why high revving 600’s can produce the high horsepower figures gaining in excess of 100bhp.
Its ability to do “work” is lower though, so shove a heavy bloke on pillion and the bikes performance will be really shoddy in comparisson to a bigger but lower bhp engine which wont feel the effect so much.
I think the important thing to remember is they are just numbers. On the road the gearing of the bike also has a huge influence and especially key to the use of the bike.
A big twin with low gearing will be great round town, lots of power pretty much instantly in low revs.
Want to go long distance on varied roads and I’d go for a nice four cylinder, smoother with power in the higher rev range where you’ll be more of the time on faster roads.
I’ve yet to try a triple, I mean to get around to it one day, but I have heard they are the best of both worlds.