Maxwell is much maligned for its long render times -- and certainly compared to a biased renderer (like Vray) it will take much longer. This is particularly true of interior shots, which would likely be your primary use for the software.
Typically I leave my final renders cooking overnight, so they usually get about 12-16 hours to get to what I would call done (typically SL 20) for a good sized render.
From my POV it really all comes down to what you need the software for -- it you are going to be doing just a few high quality renders a week then Maxwell is an excellent choice. If on the other hand you expect to be doing several per day then you should probably look at a biased solution. That's not to say there aren't studios using Maxwell for animations, where you would need alot of frames per day... they just have the computing power to throw at the problem (the full version of the render suite allows you to network computers together to speed up the process). With Maxwell the end result is the only real way to speed things up (at a certain point) is to use a stronger computer (or many of them together).
For the record I do own a few biased render engines, and while they are cool to play with, what I need for my work is what Maxwell gives... and I don't mind waiting for it.
SketchUp Pro has a few advantages with Maxwell but probably not enough to justify the expense on that alone... currently the best argument for SketchUp Pro is Advanced Camera, Layout and Dynamic Components.
Best,
Jason.