butterknucket,
To begin with,
the following information is only my opinion and therefore, you will need to weigh-out the pros and cons accordingly.
I see three main areas of studying scored music, 1) theory, 2) sight reading, and 3) sight playing. The first two
could be performed as purely rote exercises, but the third, would require the use of the instrument - obviously.
Sight reading, at least to me, involves the use of new material only, and therefore is really a one-time endeavor. Once a piece has been read, it should no longer be considered as new material but is in fact,
a rehearsed piece.
So, for sight reading, anything that contains a written score could be used. If the score contains "transposed" material, then ensure that you know how to ready such material first.
More importantly however, try to determine what your "goals and objectives" are for sight reading, and try to be as specific as you possible can.
I hope that you find this information helpful?