there is not a whole lot of differences between 17s and 19s now. However 19s tend to be the market focus now as they are much more popular. Consider that you can get a Viewsonic VX922 for less than 250 dollars after rebate. This is a fantastic 19 inch monitor. If you want budget (and less performance) you can still find ok 19 inch LCDs for under 150 bucks, although id avoid that route personally. Just remember, you cannot assume one monitor is better than the other based on size/brand. Check out the LCD review thread and see what fits you best.
The Viewsonic VX2025 Widescreen monitor is a much better value IMO. 1600x1050 widescreen with good gaming response.
*edit* And yes, both a 17 and a 19 will be 1280x1024. However the 19 inch will make things a little bigger. Honestly I dont know any reason to stick with 17s anymore to be honest, unless your on a very strict budget.