How do you want to use it?
Each have their own trade-offs....
Radars - $$$, are sensitive to environment & setup, you may not be able to just unpack it & get going - you could be getting interference & get lots of dud readings. Some also require additional parts to make them work with air rifles, so add $$$
Shoot through - affected by sunlight, clouds, some artificial lights, a right PITA to line up & stay on target, & lots of missed shots & error readings
Muzzle attached - this is the design that my chrony uses, never misses a shot, fastest setup possible
Accuracy - not much difference, even the cheapies work fine. There's the odd one that gives a 30fps low reading
Features...
The cheapie imports typically lack a lot of features, maybe only do m/s & not fps, no way to download or get data etc, no saving of info. How easy is it to change pellet weight? lots of off button combo's you need to remember etc...
The expensive ones come with features - but as usual, they have apps you have to install, then there's data privacy concerns etc...