While I generally agree with what you've said above, You aren't taking deep brake approaches into consideration. A vented canopy such as a RockDragon or a Troll MDV has been DESIGNED to provide stability in deep brake approaches, and leave you with a reasonable amount of flare to land you safely in a tight spot. I think it's wrong to base your canopy choice on the factors Tom mentioned by themselves, without considering the spots you want to land in. If your local "largish A" is surrounded by 60' pine trees, as are a couple around these parts, you will need a steep, stable approach to keep from dashing yourself onto sharp rocks or the trees/objects themselves.
These days there are many good canopies on the market, each excelling in one or two things, but lacking in others. There is no single canopy that is "the best" in all categories. Therefore, as a beginner, it makes the most sense to me to get a single canopy that performs medium well in ALL areas, and develop your canopy piloting skills as much as possible while you learn that canopy. During this time, it's a good idea to judge each BASE jump based on your current skill set and canopy's flight characteristics, limiting yourself to jumps that may well be "below" your ability level, but recognizing that you need to practice ALL of the skills in your BASE "quiver," including your landings.
That said, I think the Mojo is an excellent "all-around" canopy. It may not inflate as quickly as a vented canopy, but that shouldn't be a factor in any of the jumps you SHOULD be doing as a beginner. It may not have the "best" deep brake approaches, but it does well enough for the situations you SHOULD be allowing yourself to be in as a beginner. I personally don't care for the ACE, but many people do. I do love the flight characteristics of a Dagger, but not all do. Tom's advice of demoing many different canopies is good. Just be sure to do it in a low-pressure environment such as out of an airplane.
I think you get the point--your equipment doesn't keep you alive. YOU keep yourself alive. Develop the skills in your BASE "quiver." I guarantee if you continue to BASE jump, you WILL find yourself in a situation where you need them to save your life! (that's not a "you will PROBABLY need them," that is a "MOST DEFINATELY need them").