This a bit of a generlization ... first both are
two hander casting rods. The definition of what is a 'spey' vs. a 'switch' comes down to the rods length (and what the builder wants to call it).
Secondly it is highly unlikely you will
EVER single hand a 'switch.'** :stretcher Just my .02 cents but I refer to a 'switch' as a 2hander from 10 foot (yes you can get them that short) to 12 foot. Over that and you're dealing with a full on spey rod IMHO.
fae
Edit: As to rod length, and a guess as to the size of the water you may be fishing, I'd consider a 13 to 14 foot rod.
** The term 'switch rod' was coined here in the Rogue River Valley by R B Meizer. Great rod builder was getting (apparently) a considerable number of requests for a shorter (and lighter) 2hander rods. With the shorter rods you can get them as light as a 2/3 for trout fishing. A total gas to fish in low water Montana conditions!
fae