Unless you're planning on comparing your count with someone else's, it really doesn't matter how you count. I personally just use the UCM to count my toys. Before 2007 I used the SRM (Substitution Rationale Method), which for the most part was coincidentally similar to the UCM, but with the following key differences:
+ Multiples didn't count separately.
+ Any near variant that can be used as a "substitute" also didn't count separately. e.g. my original G1 Optimus Prime, 2000 reissue & New Year Special reissue all count as one toy, but my black JafCon 9 Convoy and Pepsi Convoy count separately as an additional 2 because nobody would get either of those Convoys as a 'substitute' for G1 Optimus Prime. A person who owns an original G1 Prime might think, "I don't need a reissue," or a person with a reissue may think, "Now I don't need the original," hence they are "substitutable" toys. So under the SRM my 5 different versions of the original G1 Prime count as 3 toys, whereas under the UCM they count as 5. I have two sets of CD ROM Convobat vs Megalligator, one loose one sealed -- under SRM they count as 2, under UCM they count as 4.

When I first started using the UCM I still also kept track of my toys under SRM... but it all just became too much of a hassle for lazy ol' me to count my toys under two different methods, so even though I personally preferred the SRM, I gave it the flick and I now exclusively use the UCM for counting.