I have BOTH the Pro-97 and the 528'.
I'll admit, the text tags on the Pro-97 spoiled me. Once you use the text tagging, you'll fall in love, and wonder how you got along with before. Now here's the nitty gritty, the Pro-97 is a bit more difficult to program than the 528. If you want to use text tags, the Pro-97 will take quite a bit of programming by hand to get even 30 or 40 set up. There is however good news! There is software, that will allow you to program the 97, fully, including text tags with your computer.
Now the bad news, the Pro-97 is rumored to not be re-banding friendly. Meaning, If/when rebanding hits your area, and you're under a Motorola Trunked system, your 97 is useless. For scanning conventional frequencies, and an EDACS trunked system, the Pro-97 is the BOMB!
If you're going to be scanning conventional, or EDACS trunked only, Spend the extra green and grab the 97.
Now, on the other hand the Pro-528 IS rebanding friendly. That means you won't have to worry about it. It has been my understanding, an experience with my own scanners, the 528 is somewhat easier to program by hand. But, the 528 has NO text tagging, and NO PL tone capability. The 528 can also be programmed with computer software.
In the end, it just depends on where you live, what you want to hear, and what features you want. If you like the idea of text tagging, and PL tones, the 97 is your scanner.
If you want a scanner which is rebanding friendly, and programs easily, then grab the 528.