For me, size is very important. I do a lot of running and biking through the hills and countryside and want to take my camera with me. The 27mm is the only one I can do that with. Photo's come out of it very sharp and the differences between it and the best quality Fuji Primes (currently XF90mm by all accounts) will be very small and only noticeable at 100% crops.
I love this lens - I only bought it to test it out thinking I'd sell it on. I won't be selling it on!