The Sony DSC-H200 has a higher effective megapixels 20.1 vs 16.1 for the Sony DSC-H90. The DSC-H200 has a better lens, better optical zoom (ignore the digital zoom), more shooting modes (including a manual shooting mode which I personally would prefer), and more resolution choices. Personally, I think the DSC-H200 would be a better choice. http/www.eyalg.com/compare/h90/h200
http/www.bhphotovideo.com/bnh/controller/home?O=&A=compareChart&Q=&ci=9811&items=846293-REG%3B%3B910800-REG
Before you make the plunge, read some reviews and take suggestions from the forum. Don't aim too low when choosing a camera. I've never heard anyone complaining that the camera they bought is too good.
Don't rule out used and refurbished cameras from dealers and manufacturers.