Great question. There's two things going on here. Bullet weight and bullet construction.
The 185 gr bullet is obviously lighter than the 230 gr bullet. The bullet weighs less and will also produce a little less recoil when fired from the same gun as the 230 gr.
The second issue is bullet construction. Speer makes "short barrel" versions of certain of their products because when a normal hollowpoint round is fired from a short barrel, the bullet will not build enough velocity to expand reliably when it hits the target. So the "short barrel" version of their hollowpoints addresses this issue with a different projectile, designed to expand properly even at the lower velocities produced by firing them in shorter barrelled handguns.