I use a monopod w/wo a Sirui L-10. I have several monopods, a Gitzo 3551, and old aluminum Gitzo reporter, and a Mo-Go Pod. The Mo-go is the fastest to adjust, but longest at minimum height. The Reporter is the lightest and most compact of the bunch.
I don't want to be a jerk, but Robin just purchased his setup less than a month ago and probably doesn't have a lot of use on it... and almost certainly not a lot of comparative experience with other options. Here's the
thread that lead to his decisions.
TBH, I don't see an issue with his choice of Gitzo and Acratech with the head used in gimbal orientation. It's essentially a pan tilt head when used like that. I just don't see the benefit of panning head function on a monopod. And I find a ballhead to be a PITA on a monopod. Basically, I think Robin's choice is functional for the needs, but a rather expensive way of getting there. (I have also used an Acratech GV-2 on a monopod)
I would definitely put a price/budget on the purchase... IMHO, you can get to the same level of durability/stability/usability at ~ $250 total as you can by spending $650. The *only* reason I own the Gitzo 3551 is because I stole it (bought used)...
In a monopod I care most about compact size. I want it to be easy to carry along even if I don't think I'll be using it. I don't care about speed of "setup," I care about ease/speed of adjustment/fine tuning. For me, this is typically done by just adjusting the length of the upper extension. I prefer twist lock for this because you can "loosen it" without completely "unlocking it," letting the weight compress the length gradually.
As far as the head goes, it adds quite a bit of weight (relatively) for little functional improvement. I vary between using no head (just a QR clamp) and the L-10. The L-10 is a benefit when the surface is very uneven and foot placement is less than ideal because you have no choice (i.e. when amongst a bunch of boulders). TBH, I use the L-10 more often than not just because I have it and it doesn't weigh enough that it usually matters.
As far as material goes, IMO it doesn't much matter... My old aluminum one weighs marginally less than my current model CF one. "Stability" is not a big deal w/ a monopod; it's really just used to offload the weight. Of my mono pods the Mo-Go is probably the most rigid/stable because it has just two sections... but I almost never use it.
I *never* use a spiked foot... it just results in a "sinking monopod." In fact, I usually use a replacement "big foot" on my monopods. I've never used those folding "tripod feet;" but I'm pretty certain I would still prefer the big foot.
Of the three, I use the aluminum Reporter w/ big foot the most and anytime "abuse" might be involved.
No matter what you choose, a monopod will never be a replacement for a tripod... trying to make it one is just going to cost more money than it's worth IMO. If you spend a lot of time set up in one place, or need stability, then a tripod is probably going to be the better answer. I hate tripods, but I still own/use them....
But, in the end I prefer to *handhold* using my SharpShooter Camera Mount (rifle stock setup). If you learn how to handhold so that the weight is supported by bone structure it doesn't take a lot of strength (w/wo a stock). I use a D4+400/2.8 supported by my left arm (I used to use the heavier 300-800). I have spinal nerve damage on my left side which has resulted in significant atrophy of my left pec and tricep, with a corresponding loss of strength. And I'm not a big guy to start with.
I'm not suggesting that handholding 15+lbs of gear is optimal; it's not. But I prefer it for rapidly changing scenarios (i.e. traveling) and moving subjects. There's also the "in between" solution of a monopod w/ tilt head belt mounted (stick the foot in a "tool pouch").