I count my CV 21mm LTM lens among the best money I've ever spent on camera gear. It's a stellar little lens, especially for the price. I also have the CV 25mm LTM lens, and it's really nice, too. I used to be a dedicated 24/25mm fan, when I shot more with SLR's- but for a single all-around super wide lens, I find I prefer the 21mm. The fact that it's RF coupled is nice; although it's not really necessary with lenses this wide, it is handy for close work. If I had to choose only one of these lenses, I'd stick with the 21.