I don't like to categorize clans into MPC and HPC. LPC/HPC have their certain categorizations but at the end of the day we're all competiting as pure clans.
For one thing that can be argued as an "MPC", MPCs have a smaller core of members and generally do not move up into the bigger pulls unless there is a surge. For example, EOP/Fi/MM/Foe/TLP have always had a big sized memberbase, however, CP/NME/Hi/Z/EF/E/Hz/W etc.. have medium sized member bases. Now, surges do happen, "MPCs" do begin to compete with HPCs, but at the end of the day, they will probably fall back down because of the amount of unreliable members in their surge, for example, CP vs EOP, NME vs EOP, and that's all I can really think of lol. If a clan closes into you, they will most likely end up leaving, or the base will stick together and go off elsewhere. You may keep some, adding to your core, but generally most do not stick around. Now there are also bandwagon members, who hop along clans when they're doing well. For example, CP's surge up to 100 pulls, NME's month of terror in May and other moments when they hit 70+, Hi when we hit 50ish with xL closing and people joining, Z at their peak, etc. NME used to have a big memberbase and still do, but they have a lot of inactive members and shizzle I guess. Zenith are probably the only clan right now of all of them I think drifting into becoming one of those bigger clans. I think all of the "MPCs" can grow, but they don't. They are limited by their effort, and why go for #1 when you can just have fun? That's a lot of people's thoughts. CP beat Fi in a fullout and CP are considered an MPC by many people, just shows a clan can step up but probably prefers not to or doesn't have the ACTIVE member base to.
At the end of the day we are all just clans, but are divided by the base of members and applicants per day, etc. Hopefully I didn't ramble on too much but maybe you guys might get my point. There are medium-sized memberbases and large-sized memberbases.
I think I went overboard.