I own both. The SP-25 platter fits in exactly the same way as the SP-15, so a little oil and a tap should work fine.
I own both and they gripp pretty tight. Both platters came off just fine hen I applied sufficient force to lift the platters. Only thing you have to worry about is keeping the platter absolutely vertical. Most of the SP-25 and SP-15 that I have seen have a table that is not horisontal, I find the center bearing is not point in the right direction, 90 degrees off the bottom like it should. I find the SP-15 is usefu for the 3 speeds it offers, but the SP10MkII is better as it is more sturdy, and also there are designs out there that allow for pitch shift.
The SP-25 is only for the one who is not put off by the 2-speed and 15/25 for the lighter weight of everything and the fact that neither is as sturdy as the SP-10MkII.
Like the previous posters, I enjoy both. My SP-25 with an Infinity Black Widow TA has suffered at my hands since 1979 and is a great combo. As Mikkelbreiler states, the SP-15 has a reputation for damage to the shaft through forcing the platter off or from shipping with it on. The SP-25 is a stand-alone deck sharing components with the SL-1200 and is just about as bulletproof as it gets.
If you know a mechanic, borrow a gear puller, or, carefully insert wedges under opposite edges of the platter and gently tap the spindle, then retension the wedges. Light oil, heat with a hairdryer, lift evenly and tap is another suggestion. Make sure to unplug it, turning it on with the platter removed will likely damage the circuitry. Or, if it ain't broke don't fix it.