Well, with using larger sci-fi models of an off-scale (1/20th) with figures of a more standardized size (1/18), you can pull it off easier - "it's a smaller vehicle." Same goes in reverse from 1/20 with 1/35 fig's - "hey, it's a *larger* model."
The SAFS kits have always appealed to me, but I've never had the money to get them.