I've had the chance to play with several of AT&T's messaging phones lately, and Propel will probably be the last for some time. I wish I could say I'm finishing with the best, but I think I hit the peak yesterday with the Slate. Propel is a cool phone, but in terms of instant messaging or email, the Slate wins by leaps and bounds. It's just so comfortable in my hands.
What's baffles me about the Propel is that I like it for everything it is, except as a texter. It's got a cool form factor and a slick look. But for me, the QWERTY is cramped. It's strange to me that, contracts excluded, Propel is $100 more than the Slate. Given the option to choose between the two phones without regard to money, I might pick Propel for looks, but the Slate would prevail for usability. Propel does come in some cool color combos, and I love the white with red trim.
Both phones have the same software. And the cameras are very similar; Propel has 4x zoom as opposed to Slate's 2x. Propel is more media friendly though, and that's probably where the line will be drawn for most users. Do you need an MP3 player in your phone, and do you want mobile video (CV)? I have a feeling that media hounds will probably go for a higher-end device anyway. But Propel does fill that niche between messaging device and media phone. I guess you'd have to hold both the Slate and Propel and go with what feels right in your hands.
Propel might beat Slate by a hair in terms of call quality, but so many factors can affect this aspect of a review that I hesitate to mention it. Maybe it was cloudier last night. I made a one-hour international call on the Propel today (don't worry PD crew, I used a calling card) and it was a bit muffled. But once a calling card is involved, I think clarity may no longer be indicative of phone quality. I had better bluetooth luck on the Slate. But again, very minor, if any, difference.
Up against the Matrix and the Quickfire, I put Propel and Slate at the top. I have very limited experience with the Quickfire, so I can't thoroughly compare it with the Matrix. If you're looking for an AT&T messaging phone, I'd say weigh Propel against Slate. Try to get your hands on a functioning device, and type several sentences. Different hands need different keyboards.