I like to use the twist type of holder at home and in work. The 400A ones can clamp 3.2mm rods ok.
I have also used this rubber type of holder. The rod is clamped by a sort of domed bolt, the electrode points down when clamped, so i usually bend it up but if the clamping force isn't there it goes round in circles.
Personaly.. if someone has put one of these rubber type on a welder in work i chop it off and chuck it in the skip....but that's just me i'm sure a lot of people get on with them ok.
I have a croc holder on the old think i have kicking about. Works fine for me, but its quite a heavy duty one, so got a good spring.
I do prefer the twist type though, all the ones at work have them on. Sometimes its possible to mis align the rod end, you do it up, then the rod falls out again
I have examples of both the crocodile type and professional twist type electrode holders.
The crocodile type came with one of my ultra cheap buzz boxes and I like the simplicity of the crocodile clamp design. I find it very easy to insert an electrode and, even more importantly, it's quite easy to tug the electrode out of the clamp in order to break the circuit when an electrode sticks. As a novice, I find this very useful.
I don't like the twist type holder at all. It takes longer to insert an electrode but the biggest problem is that it's almost impossible to tug the electrode free if it sticks. This seems dangerous and could put strain on the welder. The twist type clamp seems to have a much stronger grip. Perhaps a pro would find this useful but I hate it.
You wouldn't have to look hard to get one for half that. Google Murex electrode holder. Farnell do them fof under £7. My local Build centre Ironmongery place has them for about £4.
Edit - i've not been reading previous posts properly! See Paul's DIY welding link for a typical deal.
TBH, I don't mind the croc holders. There are some good quality ones. The shortcomings of the twist grippers are - you'll almost always have to bend the rod to get position (which isn't a problem), and they can be a bit tosh at gripping small rods.
I had a look on fleabay and they have them about £7 delivered,
What are the good quality croc holders??
The one I have has got a pretty weak spring which is the problem and the rod moves about where it doesn't have the strength to hold it when you are trying to weld.