With the explosion of canned craft beer, there has been an increase of poorly canned craft beer. If you outsource your canning, how will you make sure the QC is adequate? Some canning lines require mid-run adjustments to make sure they're seaming correctly. How much do you trust a stranger with thousands of dollars of your beer? If you have a run of bad cans, it sucks for you but doesn't matter at all for the canner.
That said, it's probably more likely that the mobile canner knows how to can better than you, so I'd say outsource before you buy your own canning line. But I'd say bottle before doing any of that.