Cabo has a lot of the same fish, water temp about the same, vis about the same as PV. The sites in Cabo are about 5 to 10 min boat ride out, the sites in PV are either 30 mins to Los Arcos, 1 1/2 hrs to Las Marietas and Chimo, and farther to El Morro. I think you may have a better chance of seeing Mantas in PV at the farther out sites BUT there are lots of rays around Cabo too. We saw many Mobilus rays flying overhead (in Cabo), to me they look like mid sized Mantas. The whales should be in the area too, they calve in the SEa of Cortez, i think.
There are lots of eels, puffers, tropicals and all in Cabo. My favourite site in Cabo is the Sea lion rock, they come out to play with you if you are lucky. I haven't heard of any sites in PV that have playful sea lions. I can't comment on Mazatlan because I have never dove there and haven't seen anything on the board about the diving there either.
One thing to note is that the water will be chilly, probably in the low 70s high 60s. I wore a 3mil long, a 3mil shortie and a hood when I was there this past Feb. The DM just had on a 3mil and she was cold.