Gavin,
I'd go with the deep ones. My seat is circular and in one section it is raised for people who don't want to be that low in the water. Also the step down into the spa, someone short can sit there as well.
There are those types that have the molded loungers, etc, but I didn't care for having to sit in a specific position with those types.
Most companies that sell them have models where you can climb into (empty) to see if you feel comfortable.
My house is all electric, so my spa is electric as well....the cost for running it isn't bad at all. It is well insulated around the outside of the tub walls, plus the 4" cover keeps the heat in.
This is exactly what my spa looks like without the deck and inside view....Morgan St. Thomas model