I don't know much about the bike but from what I have read the Concept is the best ski erg.
I haven't tried the Concept bike but it's worth considering the option of using your real bike on a trainer, e.g. https://tacx.com/
You're welcome to borrow the Nordictrack Sport ski machine we have in the basement. It's this model I think.
Last one to use it was VO2maxx.
You can also come over and try our paddling erg if you want.
The Concept 2 rowing erg is clearly nonpareil.