From my perspective, it is really hard to beat a Hobie Mirage kayak for use as a tender if you are sailing warm waters like here in Florida. If you are not familiar, they are SOT kayaks that can be pedaled as well as paddled. They are basically unsinkable/unswampable and tow with very little drag. I have a set of Garhauer kayak racks that I can use in rough weather but I have never actually been forced to use them. For boats bigger than my Nimble, the kayak could just be lashed on the bow. Neither of these storage options may be good enough for true blue water.

They sell a number of models but I would recommend the Outback (single) or Outfitter (tandem) for use as a tender. These are their most wide and stable boats but are still pretty fast. We have an Outfitter (425# payload) which gives us 150# of cargo with my wife and I onboard. The boat is stable enough that we easily board from our stern mounted boarding ladder. We are pretty athletic and can drive the boat at 4+ mph all day long, but 3.5 mph can be achieved with very modest efforts. The boats handle 2-3 foot chop well and are just as dry as many small inflables that I have been in. Because the drive units are underwater, these boats are not affected by headwinds nearly as much as standard paddle kayaks. We also have a Revo 13 (single) which is a little less stable but faster. It is also easy enough to board and I can average 5 mph. In the five years that I have owned Mirage boats, I have never captized in spite of being out (intentionally) in some pretty rough conditions. The other good thing is that the motor ALWAYS starts and I don't have to carry gas.

Hobie Mirage kayaks also make great toys. I have a sail rig which is a lot of fun and they are great to fish out of. Both both boats are stable enough that we can actually go swimming and get back aboard over the side (especially the Outfitter). They also give us a good exercise option when cruising.

This pict is from Beer 2012 in Pensacola