I have a MagnetoSpeed V1, a CED M2, and probably will buy a Labradar when available.
The MagnetoSpeed is a joy to use. Setup is a snap no matter what range rules apply. Light conditions do not matter - indoors, outdoors, rain or shine. And there's nothing you will shoot. Drawbacks are upfront cost, your firearm must have a barrel the bayonet can attach to, and attaching it is 99% likely to change your POI (there's no evidence it changes group sizes) due to changing barrel harmonics. Using it during load development means most of us make extra ammo to run separately thru the chrono.
The "standard" chronos are less expensive and can be used with any firearm. Drawbacks are setup requires going down range which is not possible at some ranges and at least requires a cease-fire so you can fine tune while other people glare at you. And that fine tuning may have to be done without touching your firearm, depending on range cease-fire rules. Light and weather conditions can affect or preclude use. Finally, you or a dear friend *will* shoot it at least once.
If you go this route, consider a chrono with a remote display to keep some electronics out of danger and bring it closer to your eyes. More expensive models that provide statistics, data storage, PC transfer etc can be done with a pencil and paper or OpenOffice Calc/Excel.
