The traditional tenders/dingy is not very stable but properly taken care of they could last years...
I bristle whenever I hear the statement about traditional tenders not being stable. Many people have formed that opinion, based on experience with some unstable designs that are out there in abundance. But there are plenty of very stable designs -- you just have to learn to distinguish between them.
Try to avoid any dinghy that has a rounded bottom and/or soft or no chine at the turn of the bilge. What you should look for is a flat- or slightly v-bottomed, slab-sided design. I tend to prefer pram-style in the smaller size-range, not only because you get more "volume" for a given length but also because the pram approach allows the design attributes that lead to stability to be carried further forward, improving stability.
The dinghy in your link might work, but it looks a bit heavy (for towing, anyway). I am not a fan of the plastic material, though. Plus, no sailrig, right? For me, lack of a sailrig option would be a showstopper on a hard dinghy. Sailing versatility is one of the great things about hard dinghies.
If you do plan to tow, I would get a first hand account of how well that Watertender does for towing before purchasing. Usually for towing, you want a dinghy that will easily get up on a plane. I have my doubts about that tri-hull.
I think you know what I like (check out the CLC Eastport Pram, or Passagemaker Dinghy). But if you don't want to build your own, the Dyers, while not prams, are stable and make good sail-trainers for kids or adults.