After years of fumbling & leaks with the old R12 pierce valves I bought a side tap. I had a can of R12 turn in to a rocket when the tap let go of the top rim as I was piercing it - that was the final straw.
1) No pierce & retract for flow - the pierce needle stays swaged in the hole as long as the tap is installed. Not a great seal, but it fully supports the secondary rubber seal against the can.
2) It fits everything. I have had a 134a can with threads so bad the valve would not even screw on it. Side tap no problem. It can't fly off - it wraps around the can. Want to access other aerosols at high volume? No problem. Got an old 4 ounce can of oil & dye? done.
3) You can pierce at the lowest point on the can, where the rim supports it. Then you can set the can on a flat surface & draw liquid. By drawing liquid you solve the freezing can issues. Throttle the service valve if you want gas, the manifold gets cold - but the can stays at full pressure.
One of the reasons I recommended it to the M-B owner is 30 year old cans. The can OD is the same, and the side tap will fit. I can't promise that there is a compatible top tap in his tool box.