It can help if you have friends who have different guitars so you can try theirs, in shops however I feel the guitar and how it sits, I shop at Sounds great in Manchester England where the have stools, chairs and even a couple of sofa's to try the guitars out on. But as you say the set up and strings that differ may alter your views. Perhaps shops should provide guitars that are for those who wish to try at home for the seriouse buyer, this could be something for shops to consider.
It's made me think, you posed a good question
While I'm sat here, Playin', I'm tryin' to free my mind!
