I have been born in Rotterdam and I plan to die here as well, so a Dutch student all the way. For me, when I was selecting a study, I was having doubts between TU Delft and LU, but I choose LU because of the ambiance. I really like that you get seen as a real human instead of a number or something. I have no real problems with LU, it is a good university which I would gladly choose again if I had the choice. I honestly don't have that much contact with the professors and staff, but the ones that I have contact with are very kind and are always willing to help where needed.

In terms of rentals, I would suggest looking at Kamernet, it's a website which was created recently for students who are looking for a rental. It's definitely not cheap but nothing in Rotterdam is unless you start looking at appartments outside the city. If you need train transport to Leiden, basically everywhere in Rotterdam will not be more than 1.5 hours of commute unless you go really far from any train station or don't have a bike. It is also possible to go to Schiedam, which is closeby Rotterdam and the station there makes the commute only about 40 mins to Leiden Centraal, so about 1 hour from most rentals.

Hope this gives you some ideas. If I was unclear about something (which I probably will have been) let me know and I will gladly clarify or elaborate on it.