I had a combo for the first 11 years, better than nothing but not most desirable. After the wash cycle if you didn't literally peel the clothes off the drum and fluff them prior to dryer running, the clothes would dry a stuck to the drum.
Our separate machine takes way less time to both wash and to dry. We also have a quick cycle. The capacity of both are slightly larger than the combo, but they are 10 year newer technology.
If you have the room, I would go with the separate units.
2009 American Eagle 42'
Trailering HD Road Glide and Saab 9.3 or Cadillac Escalade ESV