HTC Dash / S620 / S621 (Excalibur)

It really depends on what you want to use it for. For example, while both the mda and the dash have a 1.3 megapixel camera, and even though the mda has flash and the dash doesn't, pictures taken on the dash are notably better, even in the dark without the flash. They both use mostly the same programs, mostly. The MDA however, has excel, word, and powerpoint applications, while the dash only has viewers. I would like to emphasize though that with both phones, there is a plethora of third party software available at sites like handango that allow you to make your phone what you want. I personally have the dash and am in love with it. It's more phone size, and unlike the mda, you can use it with one hand. I don't really know what else you like to know, but if there's anything you'd like to know that I haven't covered let me know, and I'll try and find out for you.