Ok, what one person prefers, another may detest so let me list advantages and disadvantages of each (based on the Splendides) to help you with making your own decision.
1. Takes up less space.
2. Can run on a single 15A 120v dedicated circuit.
3. Weighs less.
4. Can do both wash and dry unattended (this advantage is negated if one needs to remove and fold clothes before starting dry cycle to reduce wrinkling).
1. Multiple loads take longer than a stack.
2. Can dry only 11 lb. instead of the 13 of a stack.
1. Larger dryer load than combo (13 lb. instead of 11)
2. Less time to do multiple loads since the dryer can be running while the next load is washing.
1. Weighs more.
2. Needs 2 15A 120v dedicated circuits (although, depending on the draw of the refrigerator, one may be able to steal the needed 4A for the washer from the refrigerator circuit) or one 20A 120v circuit.
3. Takes up more space than a combo.
If you decide on a combo, be sure to get a vented unit. The ventless use more water, take considerably longer to dry, then they don't get the clothes quite dry. Finding a way to squeeze in the vent might be challenging but it would be well worth it.
Also, if you get a combo, if the hookups will permit it (the drain standpipe would probably have to be extended somehow), consider raising the unit off the floor 12"-18". Your back will thank you for it. You can always reclaim the space under the combo with a drawer or slide out shelf. Either can hide behind the existing door.