Pro4 all the way for me. I tried the reedy 4.5 550 for 2 batteries and hated the way my truck drove especially while jumping it felt retarded, nose high always. Put the pro4 back in and I was back to driving better than ever. The 4.5 works excellent in my scte. Everyone is different, I know the 4.5 is a beast but I didnt like it in my FT SC10 4X4.