You can't go wrong with a mini skid purchase of any variety. To get on here and say that one machine will double the output of a competing machine is uninformed at worst and ridiculous at best!
We run an MT55 and it's a beast. I ran the Toro's, the Ditch Witch offerings, the Vermeers and the Boxer (the controls were terrible!). I could have made a ton of money with any of them. We ended up with the Bobcat because I found a heck of a deal.
If you're looking at a machine in the 10k range vs. a machine in the upper 20k range that may have a slightly better specs...you're dreaming if you actually think you're going to see that money come back to you in the form of greater profitability. I'd venture to say that there are less than 5 contractors who visit this site that could tell you, based on actual cost analysis, what the cost breakdown on a specific machine is.
With small equipment there are just to many variables. Sure one machine may dig a little better with a good operator, but put a new guy on it and all the productivity you gained with the good op just went down the drain. Go with solid equipment that will make you money across the spectrum and don't get stuck with Dodge vs. Chevy debates.
It's late....clearly my opinion went into overdrive. Take my thoughts with a grain of salt...or two!
good advice here! I might add that the zahn units I have run had very little traction compared to my mt55. I would get a tracked mini skid over a wheeled unit any day.