Hey Simon,
I hope I did not come across like I have been disappointed with the difference.
Number of enemies or amount of content is not a differentiating factor for me at all.
There are a few key differences for me though:
1. You have quite some quests going for you that are more than some things in an achievement/quest table that you can go and stumble upon. There is direct interaction with quest givers. That has a way more RPG-ey feeling than some "find/rescue mystery person in map XY" -> I think that's one thing this genre can really profit from. Some more interaction with the worlds and NPCs to make it all a bit more immersive and believable.
2. controls: I think while it may be a flavor for some, it is a key element for me as well - as it's basically the only thing you really do in VS. You have acceleration and braking and then steering instead of a simple "move on two axis with WASD". That creates a way more intricate interaction with the game. In combination with the "cozy" aspect this seems fine, if it was a bit more nail bitingly arcade-ey, I'd say I'd prefer the regular WASD two axis style movement.
3. the time constraints are not limited by an unwinnable boss battle but simply by the timer that runs out. I guess that's something you'll eventually change in development anyways, but it changes the whole prospect of "you die every run" vs the cozy version of it where you "either die or the timer runs out". -> I obviously only did a few runs of CSS yet, but having the timer being the limiting factor in combination with the quests I wanted to fulfill put a bit of stress on my experience. (It also added some replay value, because I never got it all done in one sweep... :) ) In comparison in VS I have a way different approach to a run where I have the overall progress to slowly work towards and in reverse I have the time I have put into a run as a stress factor as my gaming time is very limited ^^
Now That I have written it out, I think the third point will probably solve itself over time and during development, when you are going to implement some overarching run-independent progression. The second point will probably not affect the experience too much, as the focus is on the cozy-ness and thus the urge to be overly competitive with it does not get into the foreground anyways.
The first point will remain a bit though. And can be a differentiation that you can happily build upon :) It is a bit harder to develop and scale than simple "achieve X amount of damage" style quests/progress barriers. It will definitely add to the player experience though. In a very good way.