I am looking at a boat now with a drop keel. What do you think of these , I don't see any of the modern boats with them.
When you say "drop keel", I assume you are not talking about a centerboard. There are 2 basic types of drop keels: swing keel and daggerboard. There are a number of swing keel boats that have been made over the years, but when you get into the 30+ ft range, the Clearwater 35, Seguin 40, Feeling 416 DI, and Southerlys come to mind in the swing keel genre. The Hake designs represent the daggerboard option. I believe the Southerly and Hake boats are available new, but the Clearwater and Seguin are not in production and I don't know about the Feeling.
FWIW, I own a Clearwater 35, which I acquired 17 years ago, primarily for its extreme shoal draft (1' 10" with keel and rudder retracted). With this kind of draft, the anchorages are bigger, more slips are availble, you can take shortcuts others can't, and you have more gunkholing options. There are no performance compromises when the keel is down. In fact this boat is less tender and more weatherly than most boats in her size range.
The real compromise is in reduced interior volume--although I have 6'3" headroom--and a main cabin that has an unorthodox layout to accommodate a keel trunk that extends to the coachroof. You might also consider that the swing keel and swing rudder add complexity (and therefore added initial cost) with the potential for additional maintenance.
A daggerboard in the shape of a fin keel with a ballast bulb (e.g., Hake) may provide a more efficient foil than my swing keel, but would likely sustain more damage in a hard grounding than my keel (which would swing up on impact). Not to pick on Hake: a hard grounding with a fixed keel might be worse than a hard grounding with a daggerboard, depending on the trunk design. A stand-out advantage of either swing keel or daggerboard is that you could--in most cases--self-rescue in the case of a hard grounding by retracting your "landing gear".
IMHO, you would consider such a boat if you really needed the shoal draft, otherwise you ought to keep it simple. For the much of the East coast and the Bahamas, it makes sense, but perhaps not so much on the left coast.