I had a P-01 for HD use and CCW and just bought an SP-01 Tactical for range and some informal 3 gun shooting.
The SP-01 Tactical's grip fits me as well as the P-01, and is slightly longer. If you lay the pistols upside-down on their sights, the grip of the SP-01 Tactical is only a little longer, but the magazines are extended and the mag add yet more length.
Both have the decockers, which is why I chose the "Tactical" SP-01 variant. The SP-01's decocker is ambidextrous, and after using this handgun for a while, I'd like to have an ambi decocker on the P-01 as well.
The SP-01 is longer through the slide/barrel, but otherwise very close to the P-01.
The frame of the P-01 is alloy, the frame of the SP-01 Tactical is steel, so there is substantial weight difference. Because the slide is longer, the SP-01 still balances very well. The added weight helps recovery and successive shots are much quicker for me. This is another part of why I wanted the longer, heavier pistols, and my small-framed daughter enjoys shooting the heavier gun more than the P-01, which is a little jumpy for her. She already calls the SP-01 "my gun", so I may end up with another one before it's all over, LOL.
Both of my handguns have the factory tritium sights, so sight picture is identical.
The P-01 is a little thicker "someplace", so the Kydex BladeTech (DOH) holster for the P-01 is sloppy on the SP-01. I simply got another BladeTech (SRB) for the SP-01, which arrived yesterday and works great. I got the SRB because I found that the offset bracket on the DOH does not work for me and I have been taking them off. Because I am used to carrying high and tight, I always try to reholster by putting the gun between the offset holster and my body.
I have a leather Bianchi Minimalist for the Glock 17 that fits both guns fine, but may get a little sloppy on the SP-01 after it gets some more wear/stretch on it. Being leather, it is affected by belt tension and with proper belt adjustment, it fits both guns.
I could do without the light rail, which adds a little unwanted bulk for CCW, but the P-01 fit and balanced much better than the 75B Compact, and I much prefer the decocker system for CCW, so the P-01 was THE model for me, and the SP-01 Tactical is so similar, there are no transitional problems at all.
Overall, I'm very pleased with the pair.
