it would be a waste to 'just' use it as a 24, because has so much more to give.
I never tried the 24efII, but I really love the 24 ts-e. Next upgrade I will make will be the TS-e17mm
Still think Canon is missing something between 14 and 24 as worth consideing prime - they can't/won't ever have every number in between(as prime) but seem logic that they should consider a 20mm (1.8?) or whatever they can make with low CA and soft edges
Zeiss has the 18 and 21, altough the 18 is a lesser performer - so there you have it 19-1/2