Still not sure you've defined your use case. For example:
- SR has a flooding hull which makes it exceptionally stable. Great if you expect to sit at low speed / stationary for long periods (fishing, coaching, safety cover etc). The Zodiac has a built in fuel tank which might achieve similar when FULL.
- Distance being covered. The 2 stroke will drink petrol faster than a student at a free bar. But if you are not expecting to do huge hours and distances then that may not matter
- Seating Layout - any differences? Will one work better for you
- Where will you fuel?
In terms of the valuation of the boats - Are the engines the same age as the hulls? How many hours? What state are the tubes? What about trailers?
- How long will you own it?
30 min unskilled labor with no climate control to install a tubeset is nice, as opposed to spending 20 labor hours hand gluing that beast on.
But higher tube purchase price? I doubt many people in the UK glue their own on.