I am a member at MFS but that's handguns only, (technically handgun ammo only).
I guess my main issue with the sponsorship route is that it is way more of a timely hassle than what I was introduced to. On any given day of the month I can go to MFS, join and pay and voila, I'm a member and I can begin shooting right then. Sponsorships into clubs seems to be a one night out-of-the-month shot. My second issue is that, given that I'm not much of a "mingler", it appears to be a daunting task for me, (in reality it may not be, but that's just how I see it). Think about it, I'm to drive over to some clubhouse at night and enter into a roomful of people I have never met and then begin mingling with them hoping somebody will take me up as their sponsor. I'm a guy that keeps very busy with pretty cool things that I create and manufacture, but I enjoy my alone time so I guess I'm an introvert.
For guys like me I like the MFS way when I want to shoot. If they only had a rifle range.