With the popularity of the swim spa growing Manufactures are making more and more models. So the options you have are growing. Size is one of the biggest decisions to make, A swim spa typically starts at around 12ft and goes up from there.
Is the reason your interested in a swim spa more for fun vs. swim and want the versatility to have both? Money can be saved if this is the reason because there are the serious swim machine that will out perform less expensive versions. Some even made by the same manufacture. Talk will your sales person so they can fit the right swim spa for your needs
Dual tank combos are an excellent way to have a hot tub and a cooler temp swim spa all in one.