I use both Combro and Crony F1.
Crony F1 pros
Display reads to 0.1 ft/s (ie., 850.3 ft/s)
Stand alone unit
Crony F1 cons
You need illuminators if you're using it indoors or you'll keep getting errors
Bulky to carry around
Combro pros
Very portable
Easy to align if you also buy the alignment tool for it
Combro cons
Have to attach it to the muzzle (I use electrical tape, but folks use rubber bands, velcro straps, etc.)
Display rounds up to the nearest ft/s (ie., 850 ft/s)
Both are reasonably accurate
The combro is always with me when I'm shooting at the range - ve