Chris,
The Trumpter M1 kits are nicely done and an excellent value. It appears they duplicated the best parts of the Tamiya and DML kits. I find the detail a little softer than the DML kits and not as easy to build as the Tamiya kits. Tamiya's M1A1 is an earlier M1A1 and both Trumpeter and DML's kits are later, more modern M1A1s.
As far as Skif goes, their quality is hit and miss. I have several of their kits. The ones I have are the T-64b (#202), T-80UD(#201) and the infamous T-55A(#221). Their T-80 is one of the better ones on the market compared to the DML or Lindberg kits. Their T-64 series is the only game in town and the T-55 should be passed over for the new Tamiya kit.