Whats the advantage of using Lotus Notes rather then Salesforce?

I dont think there is an advantage

Whats the advantage of using Lotus Notes rather then Salesforce?
Not being an expert on Salesforce but having a pretty good background in Notes, I would say that Lotus Notes' strength is in it's ability to provide lots of different functionality. While packages might specialise in particular areas (Salesforce seems to specialise in CRM) Notes can provide a common UI for things like document libraries, email, CRM and anything else you want to program. This means that the problems normally encountered with integration across multiple different packages can disappear in Notes as it uses LotusScript (a variant of VB) and Java/CORBA to work with anything written in Notes.

You can also use tools to integrate with Notes through CORBA or SQL/ODBC.

So I guess it's advantage is that it doesn't specialise in one thing but tries to do everything at once (and how well it does that is down to the skill of each developer).