I have both and both have their pro's and cons. The tamiya was a very fun build, but in the end I missed the barrel recoil. So, I bought the Tamiya M-51 kit. Not an accurate M-51 by any means but I don't care. It's painted OD and I really enjoy it. The sounds are great also. Others have made changes to the M4 and have a recoiling barrel but I don't have the skill set to do this.

The Taigen 75 mm IR I have is a great tank too. Came with IR and a recoiling barrel. The sounds produced from the MFU leave something to be desired. That said, it's a great tank and I will purchase the upcoming 76mm in IR. I'm hoping the tank sounds will be improved. Good luck with your decision.