DW sk650 king of mini-skids....terex PT 30 also excellent, but an entirely different animal.
I own an sk650 I have used extensively a Vermeer s600tx and an mt 52.
The mt 52 sucks compared to the s600tx and the sk 650 really stands out over the s600tx. I have briefly used a dingo 425 tx to load an attachment into my truck and it has some pros, but isnt half the machine that the sk 650 is. If you were going to pull more pipe that anything else (>80% of usage) I would seriously consider the zahn. otherwise the versatility of the sk 650 will be the ticket