The reason the 106 eventually got funding was not because of increased performance but increased reliability. Unfortunately everybody expected a big increase in thrust, but that was only a modest by-product of the work that RR carried out (and which was more or less offset by the increased weight of the engine and its airframe mods at the back which had to be balanced by additional ballast in the nose, can't recall precise numbers but an increase of 200kg to the basic mass comes to mind). In answer to your question as far as reliability was concerned it was probably better than the 104 in terms of reliability as it matured but there were a few gotcha's which had to be learned about on the way. As for thrust, probably about the same, although I think accel times and handling should have been a bit better than the 104- perhaps one of the pilots will answer that bit, plenty of ex Jag guys look in here.