What it comes down to is that you need someone technically inclined that you trust
in your corner. I don't agree with throwing around stereotypes or giving broad advice. Every situation is different.
Speaking as someone that has contracted with startups and helped them create viable platforms for a fraction of the cost of hiring an employee or co-founder, out-sourcing it can absolutely work as long as you are careful with how it's managed. If you outsource, I highly recommend getting someone you trust to manage the project from a technical standpoint to ensure that it's foundation is solid. The time commitment can be minimal but he/she should have proven development experience and should be a trustworthy proponent of your best interests. This is a great option if you want to get an MVP out there ASAP and don't want it to cost a ton of money.
If you find a great technical cofounder that shares your vision and is adept enough to develop it on his/herself, great. But it will be much more costly for you to jump into bed with the wrong person out of desperation for a technical cofounder only to find that he/she is completely wrong for your business. A cofounder divorce is much more difficult and costly than firing an outside firm. Same goes for a first developer employee, but to a lesser extent.
Yes, a cofounder usually trades salary for equity, in which case he/she has more skin in the game. But an employee or outsourced firm can be fired if they don't perform (especially if you are smart about the way the contract is worded), which should really be motivation enough for them to do a good job. Anyone (even a cofounder that came up with the idea jointly with you) can lose interest. And anyone (even a contractor) can get fired up by the idea.
About the only general, solid advice I can give is that you need someone technical that you trust to manage the software project. If that person is the cofounder, an employee, or someone that just manages an outsourced firm is less important than how good that person is technically and how much you trust him/her to protect your interests.