Not sure what type of furniture you build or what specifically you will use the DTS400 for. I do own the DTS400 (but not the cordless model). I, too, am a hobbyist - furniture, cabinets, etc. Three comments about the sander...
1. I love it...No vibration...A great finish sander...Smoother operating than my ETS125 with at least the same result (maybe better than the ETS125).
2. I bought it to facilitate sanding into corners. While it certainly does that, I don't think it quite met my expectations with regard to corners. You have to be careful not to damage or wear out the the front point on the pad when corner sanding.
3. For sanders, I have never seen the need for cordless. You're tied to a vacuum anyway. Might just as well be tied to an outlet also. I use a Festool CT with an overarm and hose/cord combo. With that setup, I see no advantage to cordless. A good reason for the cordless model would be if you plan to use the sander at multiple sites or don't have handy outlets in your shop.