No, not as far as I know. The only reason you should be able to use them on the same condition is that it's a house blend where the type of ball hardly makes any difference at all.

FOr the average revs, average ball speed bowler -
The 2.5 was/is a medium oil pearl; can probably handle a little into medium+ and down into medium- oil amounts.
The Siege was their heavy oil ball at the time; yes, it will be smoother and more even reacting but unless you have medium-heavy to heavy oil, with the stock surface it'll probably burn up in the midlane and hit very weakly.

If you're rev dominant or you're speed dominant, that will all change, to one direction of the other.

If you dull the polished 2.5 or you polish up the Siege, you can force them to handle more and less oil respectively and bring their reactions closer together. Dulled, the 2.5 will, of course, be less flippy. Polished the Siege will be more angular but probably not as sharp as the 2.5.