I've got a 15 gal which I use to boil 5 gal batches. IMO, I'm not sure I can justify the added cost. If that polar ware kettle doesn't have a sight glass, then maybe. For 5 gal batches the thermometer is not very useful, but you won't have that problem.
If the polar ware kettle just has a different sight glass, then yea, save the $$$ and get something else you need.