I know this is a long shot, since you're all from USA/Canada, and I'm from Europe (so appliances are vastly different), but maybe there is some general advice you can share...
We live in a small apartment, and space is really constrained. We don't have room for 2 separate devices (though maybe it would be possible with some kind of strong metal shelf so that we can stack them, but that's a pretty wild idea). Also, we don't have enough free money for both (and we have no desire to take on another loan).
So far we've made do with only a small washing machine (3.5kg max load or something), but it's obvious that it's too small, especially since our second child will arrive soon. We're already doing about 2 cycles daily. Also, during the winter we cannot hang dry the clothing outside on the balcony (and we're short on space inside), so we're thinking about getting a washer/dryer combo, which would help out. The dryer would need to be the condensing type, since I won't be able to attach it to the ventilation system.
The advice I've found on the Internet so far is uniformly "two devices are better than one". And while I don't seek to disagree, I wonder if a single device can be efficient too? Or is it really so that a washing machine without a dryer is better than a combo? Anybody have any experience with this? Any brands maybe you can recommend? (Miele would be out of my price range)