I see that my initial/current display method has earnt zero votes so far - I've been displaying the combiner teams in their individual bot forms, as the combiner form was really just a gimmick originally... and it helps with the counting/numbers, as the individual bots were the default characters (in the cartoon and comics, they were rarely combined, spending more time as the individual bots).
But since combined modes have grown into an impressive, fan-favourite concept (that Hasbro loves to milk), it's now starting to appeal to me as something to display in addition to the individual characters we actually see more of in cartoon & comics (which my collection features).

The comments and voting has certainly given me a lot of insight into this though.