I voted for MPC for the reasons of;
Estes mass produced and will be readily available for a long time.
Centuri as a kit is a collectable and value is in an unopened kit.
MPC has little collection value, they are out there and are cheap. They fly just as well as any other.
I would love to have the Centuri Payloader II. I have an Model Rocket Industries (MRI) Zenith II kit, which became the Model Products Corp. Zenith II which became the Quest Zenith II. I actually have two or three of the MPC kits and started building one. Their T-25 tube is similar to the Estes Bt-50. The 4" clear plastic payload section tube had shrunk in diameter over the 4 decades or so since it was kitted. The clear tube from the Estes Payloader II fits just fine.
Estes and Centuri were not and are not the same. The Centuri Payloader II was based on their ST-10 tube (available from SEMROC at eRockets.biz) while the recently release of the Estes Payloader II is BT-50, which is slightly smaller than the ST-10.
I started with Centuri in 1967 and then added MRI and Estes. Both Estes and Centuri were purchased in the early 1970s by Damon Corp. Later on the Centuri kits were phased out and/or adapted to use Estes sized parts. You can see the Centuri influence in some of the recent Estes offering, especially their reworked Saturn V kits.
I voted for the Centuri Payloader II mostly because when I was a kid all of the hobby shops in my area were strictly Estes so Centuri stuff was the cool forbidden fruit. There was one shop a couple of towns over that carried a few Centuri kits, but we didn't get that way very often and when we did a stop at the hobby shop was rarely on the agenda!
MPC was also a no-show around here and had some really cool kits, but that particular one never really appealed to me.
I started the first time in rockets about 1980 with an Estes Alpha III (or was it II?). The only thing I knew was Estes until I joined a club - the Summit City Aerospace Modelers (S.C.A.M.) in Ft. Wayne, IN - and learned about Centuri motors, but nothing produced by Centuri was available in my neck of the woods, it was all Estes. To me, the MPC model is a completely different model, and only shares the name. I'd take the Centuri kit.
MPC Zenith two payloader. Because I built one of those in 1970 or so. Indeed the first one I built may have been an MRI Zenith Two payloader. When Mike Bergenski sort of merged (?) his Model Rocket Industries (MRI) with General Mills (do not know the business details) in order to create the rocket division of MPC, that MRI kit later became an MPC kit. I still have an MRI zenith two in storage.
And by MRI Kit I mean old-school hang-tag style, like Estes kits were around 1969. The MRI kit had a hangtag and a "facer" card inside. A cannot google an image of the kit, the kit I have is not accessible.
The MPC kit came out later, in a box like most MPC rocket kits.
Of course later on, Quest brought it back yet again.