To WordPress or Not WordPress?

Hi,
I’m currently rebranding and having my website redesigned and developed.
At the moment, it’s largely written in classic ASP, with some elements written in ASP.net.
My developer wants to go ahead and write it all in .net as it says it makes for far less work.
However, another web guy who is a friend of mine advised me to move over to WordPress but I’m wondering if it will do all that I need to do and how customisable it will be.

It’s a membership website and while at the moment, there are no social profiles, it will likely go that way in the future. Right now, it’s just about signing up as a member and booking on to events.
Much of the functionality is at the back end where we have records of events booked etc. but also a system which tells us what’s been happening in terms of sales and marketing e.g. if someone has booked on to a free trial, we have a trigger to remind us three days after the fact, so that we can give him a call and attempt to sell him full membership.
I just don’t know if WordPress will be able to handle all of this, and similar.
If so, would it be off the self solutions, customisable scripts, or a combination.
I would appreciate any advice on it.
Thanks, Steve