Watch the electrical interconnections. On some units, particularly those used in dense condo developments, they use "very special" units which have features that reduce the number of utilities that must be brought to the washer-dryer nook.
- Dryers that provide electrical to (and coordinate with) the washer: eliminate sthe need for a 120/240V circuit
- Washers which heat the water: eliminates need for a hot water line
- Condensing OR heat pump dryers: eliminates need for exhaust vent
If you don't pay attention to those details, you can bring a new unit home and find nothing to hook it to. Happens all the time.
So long as they're the same size - width & depth, there shouldn't be any problem. A lot of the stacking brackets/mounting rails for stacking units are universal anyway, if you want to go that route. Something like this, from Amazon:
FWIW, my new dryers is just sitting on top of the washer with no brackets.