Depends what you want and how often you’d use it.
I’d say if the Carista can do all the things you want, then at £15 on amazon which includes a month free when you register, is the way to go.
If for you Carista doesn’t do everything you want, and you plan to use it a lot, then OBD11 is the better choice.
I only have an iPhone so Carista was my only choice. It’s done 70% of what I wanted it to do:
Done all this:
1) 1 click auto fold mirrors.
2) Sound Actuator turned down
3) 4 indicator flash’s on tap
5) drip wiper sweep a few seconds after washing windows
I still want to change my door lights to always be red, have my rear lights on with my DRLs, and then on the road sign recognition on (my car has all the other bits to enable this).
Carista doesn’t do these
(yet?) but then OBD11 isn’t on iPhone