They both have their plusses and minuses.
If you only want to fly it with 54mm rockets and larger, the Marsa54 has a number of features that the Raven doesn't have, with the LCD screen being probably the most significant. Their front page has a bunch of questions about features in which the Marsa54 people have gone a step beyond what the Raven does. You'll have to decide how important those distinctions are for what you're doing. The Marsa54 also has an expansion connector to use it with future modules, particularly GPS. If people want, I could discuss each of their questions on the front page to describe the Raven's alternative to the Marsa54 approach, but it could be tricky for me to do that from an unbiased perspective.
The things that I know the Raven can do that the Marsa54 can't, are
1. Fit in 24mm, 29mm or 38mm rockets.
2. Less expensive; Marsa54 is 45% more expensive than a Raven.
3. 0.05% accuracy barometric sensor that works up to 100,000 feet (vs. 45kft)
4. Higher G-range standard accelerometer (70 vs 50 Gs)
5. Higher high-range accelerometer available (250 Gs vs 100 Gs)
5. Lateral acceleration measurement
6. Fit into 2" long, no-wire av-bays available in 24mm, 29mm, and 38mm.
7. Use a single lipo cell for power and pyro deployments (rather than a 9V battery)
Some things that I don't know about the Marsa54 altimeter that I'm curious about, if someone has the information, are:
1. What are all the recorded data measurements? Does it record battery current, battery voltage, continuity of each of the channels, and temperature? Does it record all derived flight events, whether or not they're used for the deployments? The Raven does.
2. What is the time resolution for the different measurements? The Raven records the axial acceleration at 400 Hz, the lateral acceleration at 200 Hz, 40 Hz for the battery current, and 20 Hz for everything else. This is useful for seeing what happens during deployment and landing events.
3. Does the Marsa54 have a motor burnout counter (very useful for multiple airstarts)?
Each altimeter manufacturer has his own ideas about what features are important, both to themselves, and to their customers, and has designed an altimeter that is optimized around those features. It's interesting to see how different those priorities are, once you get past the basic dual deployment functions. Each has his own niche and I'm glad that the Marsa54 exists so that people don't bug me about making a Raven with an LCD.
There are altimeters being sold now that fall short compared to the Raven in almost every category, but the Marsa54 isn't one of them.
