I'd go with the H5450 because it has bluetooth and I'd use that, and since i have an SD card (256MB card that I never fill completely) then the cost of memory isn't a problem. I got that SD card for around $130 towards the end of last summer. Check out
http://pocketpcthoughts.pricegrabber.com to search for low prices. A 128MB CF card is $30 on there, and a 128MB SD card is $37, 256MB is $62 ($47 for CF). SD is more expensive, but it is smaller, and has a faster read time than CF depending on the brand.