Another very similar thread about possibly upgrading from Q559 to either Q45 or S40 can be found at
https://forum.cruzbike.com/threads/thinking-of-upgrading.13187/
Here's my synopsis. But before my spiel let me agree with the above posters that based on your descriptions of your current riding, conditions, frequency, road surfaces that you would prefer the S40. The only thing you haven't comment on it seems is whether $ is a big factor. If $ is not prohibitive the S40 is more performance. Q can be made more performance than stock but can't get to the stiffer, lighter frame of the S40.
Q559:
-possibly front suspension depending on the version
-Well maintained, solid pickup truck/SUV
-grass is always greener...
Q45:
-stiffer front end (more efficient, better steering, lighter?)
-longer rear shock travel and more standard size shock (even cushier ride, more options to upgrade)
-comes with and possibility for bigger tires,
-same Mountain Bike componentry
-can be disassembled for shipping / car trunk quite easily
-only 56% the $ as S40 leaving ample room for upgrades (but can't upgrade the biggest impact on overall purpose = frame)
=serious name brand SUV or new pickup truck (definitely not old farm truck)
S40:
-same front end as Q45 (more efficient, better steering, lighter?)
-no rear suspension (but longer and bigger tires so this might not impact depending on your riding surfaces)
-comes with an possibility for bigger tires (maybe not as big as Q but if you get the S you are not likely wanting THAT big of tires)
-Road bike componentry
-lighter weight
=Fancy Sports Car/SUV eg. Porsche Macan Turbo
V20:
-nothing spared super sports car eg.Ferrari
I guess some part of the decision is: do I want an upgrade with similar or a different purpose = fast touring. (I guess that would more accurately just say "fast.".)
Am I keeping the Q559? How much $ do I want to spend? That is, does the difference in $ force the decision? Will I always regret not getting the xxx?
And are there ones in your neighbourhood that you could test ride?