Whatever its other flaws may be, if your SP10 mk2 cannot hold pitch with piano music, it's not working properly. Have you had it serviced since you bought it, or do you know whether it was serviced prior to your purchase? Proper service should include replacing all electrolytic capacitors that have not already been replaced. Same goes for your EMT or any other vintage direct-drive.
You are probably not going to find too many responders who have actually owned a 938, or even a 948 or 950 and also owned the other TT's you want to compare to the 938. I'd suggest that you have a competent technician service both the SP10 and the 938 (if you have not already done so), and then go by what your own ears tell you to do.
As an aside, I have to wonder why you sold the Redpoint if you liked it so much. Budgetary concerns would not seem to be a factor in that equation.
You are probably not going to find too many responders who have actually owned a 938, or even a 948 or 950 and also owned the other TT's you want to compare to the 938. I'd suggest that you have a competent technician service both the SP10 and the 938 (if you have not already done so), and then go by what your own ears tell you to do.
As an aside, I have to wonder why you sold the Redpoint if you liked it so much. Budgetary concerns would not seem to be a factor in that equation.