Nick, For economy, the 175. But I use a DP-420 "Hydrocare" which is similar to the Multiwash line. Here's why: Wood floors need to be deeply scrubbed with the grain and along the edges of the boards where stuff has been accumulating. A Floor wand would work fine and if you already have one, use it.
But a machine that wets, scrubs and recovers all at the same time is invaluable and is a low impact and low moisture process.
I've no experience with the machine Interlink sells for hardwood care, but you can see why it would work. However, A Multiwash would give you the muscle to do VLM on carpet, or just pre scrub for extraction.
I guess a quick scan with Searchtempest would help you see what is out there. In my case the Hydrowasher happened to be nearby for only $600. Couldn't pass it up and have never regretted it.