Here's the Phonescoop side-by-side comparison
I only know about the comparison of the similarly sized and spec'd Razr M and the Lucid 2, which I eventually purchased. In short:
- dual core processor
- 8 GB of storage
- 1 GB of RAM
- micro-SD slot
- no app-to-SD capability
Razr M has:
- international radios
- Apt-X bluetooth codec (wired-like quality when paired with headphones/speakers that support Apt-X)
- more substantial look and feel (somewhat subjective, but most say this).
Lucid 2 has:
- removable battery
- wireless charging (with optional and bulkier wireless charging back)
- full-time 4.3" screen (Razr M's 4.3" screen is occluded at the bottom by about 0.3" most of the time by its virtual navigation buttons).
If the non-replaceable battery of the Razr M is a concern, I saw once on the Motorola site a charge of something like $53 to install a new battery, which is quite a fair deal if they still offer it when your battery starts dying. Though you might not like being without your phone for the replacement time, nor sending your phone with your personal info to Motorola.
Personally, I chose the Lucid 2 because I knew I wouldn't like anything less than a full-time 4.3" screen, love wireless charging, and strongly prefer a removable battery. I miss most the Apt-X codec of the Razr M, though.
You might get more knowledgeable responses if you also ask this in the Device/Carrier Comparisons sub-forum of the Android Lounge forum.