Maybe this will help on head choice:
Pan/Tilt: Pan tilt heads provide an infinite amount of positioning by virtue of the three separate axis of tilt available. Each axis it set independently of one another in a separate movement. Most pan/tilt heads will have 2-3 levers or knobs, one for each axis.
Pros: Excellent for making small intricate adjustment on a stable platform.
Cons: Bulky to carry around due to the extended levers, and slow to adjust since each axis must be adjusted independently.
Suggested Use: Studio, portrait, static close-up/macro photography.
Ball Head: Ball heads provide a near infinite amount of positioning similar to a pan/tilt and in most cases is comparable to a ball head in the ability to position. Ball heads come in a variety of grades from the basic with one ball tension release for positioning and panning, to better ball heads with a separate panning release mechanism that does not affect the ball position. The best ball heads have separate ball lock knobs for changing position, ball tension knob to keep the camera from flopping around on a loosened ball and a separate panning knob to allow the upper part of the ball head to rotate with out changing the ball setting. Good ball heads will have short shafts extending from the ball to the camera plate for greater stability.
Pros: Excellent for general photography. Compact, easy to carry around and very quick to adjust positions.
Cons: Basic and ball heads with out a separate ball tension knob are tougher to make fine adjustments with. They also tend to have some ball creep when locking the ball head into position. A top quality ball head will usually resolve this issue and allow for finer adjustments with out creep.
Suggested Use: All around general photography. Can be used in most situations that do not require very precise adjustments.
Handle Mounted Ball Head: Handle mounted ball heads are ball heads with a handle grip release instead of a ball lock knob. Their range of adjustment is comparable to a standard ball head. Handle mounted ball heads support medium and small weight loads and are not designed for long glass or heavy gear.
Pros: Very easy to adjust with a single hand in one quick motion.
Cons: Bulky due to size, lighter maximum weight loads. Bulky to carry around. Vertical handle ball heads are less stable due to the height of the camera plate above the ball in comparison to horizontal handle ball heads. Usually lack a separate panning feature
Suggested Use: Studio/Portrait work
Gear Heads: Gear heads are precision adjustment heads on using a gear and knob system to change orientation. Their range of motion is less than most ball heads but very precise. They are usually two or three axis gear heads.
Pros: Very precise adjustment possible with minimal difficulty.
Cons: Very slow to adjust, limited adjustment range, heavy, and usually quite expensive.
Suggested Use: Precision photography where miniscule amounts of adjustments are needed.
Gimbal Head: Gimbal heads are specialty heads designed to take larger lenses with heavier loads. The usually have one or two vertical support arms and the lens rests on an extension from the arm(s). Range of motion with a Gimbal head is virtually unlimited. Gimbal heads by their nature are larger than other heads to support the weight of big glass.
Pros: Excellent for large glass. Very quick to use as the controls can be left loose for fast movement.
Cons: Bulky, heavy and expensive. They require larger sturdier legs to support the weight and are heavy carry around.
Suggested Use: Nature photography or any time large glass is used and needs to be adjusted quickly.
As for purchasing a legs and heads I would suggest two thing. First read this article by
Thom Hogan. You do not have to spend the kind of money he does, but his point is valid.
Second, buy a setup that will support at least twice the weight of your heaviest gear that you have now, and plan on buying in the future. Most photographers will end up with more than one setup depending on needs. I have three, a studio tripod, a general use tripod and one only for large glass with a gimbal head. The general use tripod gets the bulk of the work and is a set of Manfrotto 3021XproB legs that are the predecessor to the 055 legs.