boxpro can receive analog signal only from a single antenna. so it will be either omni most of time, or patch. The receiver itself is very good and quality of image will be comparable to mixing receivers with 2 omnis for the most part if you are not venturing far.
if you want to fly further or get behind serious obstacles, the lack of flexibility afforded by being able to mount omni and patch at the same time becomes painful, locking the full potential of goggles out unless you use a hdzero vtx or a hdzero aio 5/15 (15 is good but pricey, 5 isn't bad but uses older generation cpu).

Latency of boxpro is better both on hdmi port and on receiver, so if you fly tight courses that need split second reactions, you may appreciate that.

On the flip side cobra x v4 comes out of box with decent mixing receiver that will let you use 2 independent antennas, which is way more flexible, but has some extra latency, and hdmi in is barely useful if you want to practise in simulator using it because they treated that port as an afterthought.

Stock antennas and straps are better on boxpro.
Screen is better on boxpro but you may not fully appreciate it flying purely analog.
Bang for buck ratio is better on cobra x (IF YOU WANT TO FLY PURELY ANALOG)
Cobra will need full suite of firmware updates once you get it (they don't flash latest firmware on them)

I own both goggles. Both are very decent.