Movement from R-134a to HFO-1234yf is due, at least in part, to the global warming potential of 134. I understand that there are plenty of people who disagree with the research behind global warming and the ozone layer depletion. My advise for those is to do your own research. Look for studies on gradual changes in the ozone's condition (infrared photos taken over the antarctic for example). Examine changes in the weather patterns over the last 50 years, mostly relating to weather extremes rather than just "warming". If you don't find enough evidence to support the claims, then feel free to disagree. I'm not a scientist so I can neither confirm nor deny the claims. Personally I'm just looking for something that has R-134a's cooling capacity with R-12's heat disapation ability.
Most SNAP approved alternatives contain R-134a as a component. While I can attest to some improvements in performance using SNAP alternatives (used Freeze-12 myself once upon a time), if you use a variable orifice tube, you can get just as good results with R-134a. That and it won't invalidate your warranty on any replacement components. I know the alternates claim they will honor the warranty if the part vendor refuses the claim, but has anyone ever put this claim to the test or found it to not be a huge hassle? I'd love to know.