They may say they are the same grind, but the various grinds have evolved over the generations of Vokey wedges. A SM5 grind may not play the exact same as a newer version. Also, weight distribution has been changed dramatically in the last two versions, so that will impact the trajectory. Best bet is to get a proper wedge fitting to make sure you're getting the right wedges for your game.

The SM9 fly lower and bite harder.
For me it's 3-5yds lower flight from my SM5 60°

I concur with the two replies above mine. The CG is raised, resulting in lower flighted shots. I was fitted for mine at TPI in Oceanside mid-March, and just received them. Love them. The point about the grind is very true. So glad I got fitted. Enjoy your new wedges!