I have tried different PA products but for me, Micro-PA worked best to be honest. I used to hate Biotest before but they are pretty good. Quality is top, Perfect doses +++.Back to the OP's question, Danes has tried multiple PA sources and I believe he's partial to the already mentioned Micro-PA. Good to get his perspective as well.
I always felt difference betweeen Muscletech PHospha Muscle and Micro PA even they both has MediaTOR (50% enriched PA from SL).
I really didnt understand why I felt more from Micro PA (tried many times and different combinations) until I found Micro Pa contain SEDDS delivery method actually.