Optical chronos occupy the value price-point (and higher of course). In return, you carry the chrono along with its tripod, assemble and set it up when the range is cold, re-adjust it the next time the range is cold, shoot through a narrow window, miss the occasional shot when the lighting changes, and call the vendor for new parts when the inevitable drive-by shooting occurs. It's virtually impossible to use at most indoor ranges.
I have one, a CED M2, and it works very well . . . on the right days . . . outdoors . . . despite having been wounded in action twice.
Next up the price ladder is the MagnetoSpeed. Fits in your range bag, attaches in seconds, sets up when the range is hot, readout is right on the table, can be used in any or no lighting, can be used in any weather, doesn't miss a shot, and although it doesn't move much it is really really really hard to shoot it. The drawbacks are few but significant to *ME*. You must be able to attach it to your firearm, and when you attach it to your barrel you will change the POI. The V1 also consumes batteries surprisingly fast.
I have a MagnetoSpeed V1, and make extra ammo to chrono during load development. It pushed my CED M2 into virtual retirement.
At the highest price point (so far) comes the LabRadar. The promo for it says it has none of the above drawbacks. The design and method of speed measurement says that it *should* have none of the above drawbacks. If it works, I can chrono ALL shots fired during load development for any firearm, and I find that data quite useful. It also can provide some downrange data, though I'm not sure that data has any real value to me.
The reviews I'd be interested in would test battery life, try hard to determine what makes it miss shots (if any), determine how many extra shots are recorded at a crowded range (if any) and under what circumstances, etc. These will only come with some extensive use by a competent operator with no commercial bias.
While helpful, I'm not satisfied by a review that uses it once and talks mainly about whether the LabRadar is a better value than an optical or the MagnetoSpeed. Because that kind of judgement depends very much upon the individual, and how they value dollars versus doing the job . . . dollars vs relative drawbacks, etc..
So I've decided to "review" it myself Given the shipping "schedule", probably won't be until November. Can't wait . . . should be fun.