I actually like the liquid as opposed to solid... "solid" tends to burn a bit faster and does not usually have the ability to restart (except for the hybrid)....great for ballistic missles, hard to manage to precision aerial vehicles. Solid fuel seems at first glance to be easier to engineer... but looking more closely requires specific design characteristics for a manned vehicle (without boosters) that would need specific control inputs among other things.
As far as safety goes, I would favor a liquid fuel.... once a solid goes uncontrolled, that's it, game over.