Yes you would because a MS-70 (even a satin finish) is a LOT rarer than a PF-70. And that one graded MS-70 will most likely be worth multiples of what the entire mint set is worth.
This is just my opinion, but if you want a MS-70 PF you will be better off just buying one already slabbed than trying to get one yourself. You could try as Green18 stated the "crap shoot". You could send five in and two come back as 70's or send in a hundred and none come back as 70.