An 1898 rear sight would be nice from a collector's standpoint, but if you plan on shooting it, then I would opt for the 1902 instead.  The 1898 sight was calibrated for a hotter round that was eventually removed from service, and would not be as accurate when shooting ammo at normal velocities.  Plus, the 1902 usually has the pop-up Sgt. Peep which can aid in accuracy.  This is of course all dependent on if you have the proper handguard for the 1898/1902, as stated by others.