The XLR jack is more physically robust, and is a locking jack. This is true.
However - here's the thing - guitars and basses operate at low signal levels (as compared to line level) and at high impedance (also known as Hi-Z).
Microphones, on the other hand, operate at low impedance, or Lo-Z. A common misconception is that if you had an XLR out on your bass, you could plug right into a mixing board without a DI - this is not the case, as mixer XLR inputs are designed for use with low-impedance mics. For this to work, you'd need to have a built-in DI - while this could theoretically be useful, I would advise against it, just because a really good DI can cost hundreds of dollars - just get one and bring it to all your gigs, rather than get five or six and install them in all your basses.
In general, simply for reasons of simplicity, I would reccomend sticking with a 1/4" phono jack (also called a 1/4" TS or TRS) - just because it's compatible with everything there is. Bear in mind that if you used an XLR out, you'd need an XLR-to-1/4 TS/TRS converter, either in adaptor, specialty cable, or stompbox format, thereby negating by inconvenience any advantage gained by the more robust jack.
If security of connection is your prime concern, you should consider the option of the Neutrik locking TRS jacks - these plugs accept a standard instrument cable, but have a locking mechanism similar in utility to an XLR.
Hope this helps!
EDIT: Gio S, the combo jack is a good idea. The phantom power idea is also interesting, however you should bear in mind that most onboard systems used in basses (as far as I know!) are not configured to use phantom power - and also, standard microphone phantom is 48 volts, while onboard EQ/pre systems are typically set up to run on 9 or 18 volts. Not sure if that will make a significant difference, but I'd be leery of trying it, myself.