I own a 2002 Pro-Line 17 foot CC. It is an OK boat for the money. Not a bottom of the line cheap boat, but not top of the line either.
Some of the things that bother me about my boat are the hatches. Tiny which make getting to the internal hull very hard to do. I would have liked more and larger hatches in the deck and lots of access.
The next thing I would change is the interior of the hull, which is very rough. The glass work is so rough, that you have trouble cleaning it. I got a number of fiberglass splitters while working on the boat.
One last complaint. The boat doesn't drain well. Either does the motor well. Maybe I'm paranoid, but when I'm washing the boat down after a day on the water, my feeling is the boat should drain quicker. If the motor ever quit and I took a wave over the stern, I wonder how fast the boat could drain the water out. Also the ****pit drain is only 1 inch or so above the water line. So if a big wave did fill the boat with water, I wonder if the ****pit drain would be below the water line. Then I would have to rely solely on the bilge pump.
If there are gel coat issues that will show up as the boat gets older, I cant say. The fit and finish on exterior of the boat is excellent.
The ride isn't bad for a 17 footer. In fact it's quite good. I was surprised how dry the ride is. However, I can't compare my ride to yours. A 21 should ride much better. Bigger boats usually do.
One last comment. Bigger is better. If money isn't an issue go with the bigger boat.