Fit is fine and enjoyed paddling them both when demoed on relatively flat and calm water. Interested in what others think about comparisons of them in varied conditons and what one might expect. Stability, tracking, manuverability etc.
Don’t Know About Ellesmere But…
I found a significant difference in handling in rough conditions between the Tempest 170 and the 165. I do a much better job of controlling a 165. I'm 5'9" and about 165 pounds. Also my taller, heavier buddy likes to roll my 165 'cause it's so easy.
I owned anEllesmere
for a very short time but it was to “lively” for me in 2-3 ft rough water for me. I now own and paddle a NDK Explorer. A friend has a 165 and was handling the same waves just fine when I made my descision about getting rid of the Ellesmere.
Others will have different opinions 
Lively
I haven’t paddled the Tempest, but I have paddled an Ellesmere numerous times in varying conditions.
The Ellesmere is a lively hull. For me that is one of its attractions. I found it a very capable boat in challenging conditions. It is a somewhat more demanding boat than some (especially the Explorer) in return it is also a faster boat than most ‘Brit style’ kayaks.
Yep
slow and steady, that’s my style I’m to old for challenging anymore
Play with both more
Opinions from others,(mine included) while well meaning, I think are too subjective to be really useful other than real general tendencies. I believe that if you paddled each boat on a two or three day trip with varying conditions loaded and unloaded one would jump out at ya. I think it’s worth taking this effort given the cost of a kayak. Have fun.
Also in wind
Yeah - they are kinda different boats and while both will handle stuff fine, they do it in somewhat different ways. I’d add to get out into to some decent wind - 10 knots or more - with the Ellesmere if you can. It was in some wind that I discovered whether I was a best fit for the boat.