i have no experience with the dell devices you mentioned.
but i did get my brother an ipaq h4155 and it's great.
it is really small, powerful and wasn't that expensive.
(well ... i got it for free from a wonderful forum called pocketpcthoughts

) but even if i hadn't won it, i would probably have gone with it.
it's priced ok at around US$400. there is a cheaper version available, i think it's called h1940 which is a lot less expensive and still really small.
my suggestion is always to go to a store and play around with the devices and find the one that you enjoy most.
because pictures on the net and reviews can only give you a rough overview, the look and feel needs to be evaluated in person.
update: yes, it's the h1940 and it's around US$225
specs:
http://www.dealtime.com/xPF-Compaq_iPAQ_Pocket_PC_H1940
man .. this is the fourth edit. i can't seem to type numbers properly today
