I'm not a tax accountant nor am I adept at the tax laws, but I assume the reason for the difference is that an IRA is an Individual account (hence the name).

With a 401k, you are part of an organized plan that has met IRS qualifications. If you are self-employed, you might be able to set up a SEP plan to try to sock away more money, but, in all likelihood, you would have trouble qualifying it as a 401k plan.

The limit for annual contributions on a 401k is also much higher than an IRA. I think it is almost double.

Finally, a 401k may or may not allow you to borrow against it. Not all plans allow borrowing.

Hope that provides some helpful info, but, as noted above, a qualified accountant could probably explain it much better,

Not necessarily. Depends on the type of ira. Some allow contributions up to $49,000.

Sadly, our country puts a limit on retirement savings.

You can't take a loan from an ira. You can borrow from certain 401(k) plans.

Don't touch your IRA or 401k for non-retirement withdrawals period...
 

Nothing more to say, folks, it's a bad idea.

You cannot borrow from IRA, but you can invest money from your IRA in your own business (there are certain strict limitations though - google "Invest IRA in own business" and you will find plenty of information about it).

I'm not a big professional in IRAs - so don't take it as a tax advice and talk to a tax professional first - but theoretically you can invest in your own business (well, it will not really be "own" as you cannot own more than 50% and you cannot take your spouse/children as co-owners) and then borrow from this business (make sure to borrow at market interest rates - doing otherwise may very well raise a red flag with IRS) invest in BankDirect and pay your business back cash interest.