I run a Judson truckmount and have two portables. However I would not say the Portables are a backup. Different tools for different jobs. I have a self-contained walk behind that I basically only use in a couple furniture stores that I do every month. I have a tag along that I used to go up the elevator or behind locked doors.
Truckmount way to go. Where were based their isn't many high rise but generally if there are it's all stairs and parking is shocking. That's how I started out was only able to do 3 jobs a day as start up and shut down take longer than the actual job. In city porty all day long In 7 years haven't knocked back many jobs. Each to their own