both of these are excellent to stack together... osta is going to have less sides than s4... they are both extremely effective but s4 may be slightly more effective... you will get great lean muscle and a lot of strength gains... ostarine specifically is excellent for pct and stacking the 2 is great for a bridge in between cycles... s4 has the vision sides, but if dosed properly, this should be avoidable... I would recommend stacking the two together and running ostarine 7 days a week and s4 5 days on and 2 days off... dosage is the key... if you experience sides, lower the dosage until the sides stop... these effect everyone differently... they are excellent but needed to be used cautiously and properly... uniquemicals.com is a great place to get these sarms... they will take good care of you...