Hi Matt,
1. BP-MBRCPF-CC3V3 and BP-MBRCPF-CC3U are Rotary Fitting,
that G1/4" thread can be turned rotary. BP-MBCPF-CC3U is not rotary.
2. The difference between BP-MBRCPF-CC3V3 and BP-MBRCPF-CC3U is the cap.
The cap of BP-MBRCPF-CC3U is longer than BP-MBRCPF-CC3V3, which can cover the gap between the tube and fitting. They have nearly the same function.