minki,

A quick sanity check before narrowing down for a combo would be how many ppl in your household and if your home has limited dry area balcony space or none at all?
Combo washer & dryer have certain limitations:
1. Drying load is less than washing load. (8/5, 7/5, 9/6, 10/6, 11/7 etc)
2. When load piles up esp when coming back from long trips or more commonly due to lifestyle that washing can only be done over weekends (no maid or helper), have to wait for drying to complete before the next washing cycle can begin.

The other technical limitation is laundry area of homes are commonly supplied with a 13A point. Depending upon the energy requirements of a washer dryer combo, some could require minimum 15A or 20A electrical point though newer generations one less. Dedicated washer dryer should be using higher if they are used simultaneously. Just like electric ovens.

Of course, the best is to spread out washing and drying but limitation 1 is the main cause of laundry pile up in a multiple occupant household. If you're just alone then it shouldn't be an issue.

If these two limitations are not acceptable, the best is to go with separate washer and dryer. Most would supply a stacking kit.

If there's a dedicated drying area that you're able to hang laundry, there's less need for a washer/dryer combo. In that case, aim for a 1000rpm or higher spin rpm (for dryer clothes) front load washer and size up your load accordingly.