Does Studer A810 really sound better than Otari MX- 5050 BII2 ?

yes, but the big difference is the tape handling. The transport on the studer is much easier on tape. Same would be true with the MTR-10 and 12. And the sonic differences betcome moot if an outboard tape head preamp is used such as a Doshi or bottlehead etc. 

Outboard tape head preamp, preferably tube, would be the next step, the ultimate set up.