Here are some things to consider
At the mic it depends on the battery supply vs
phantom power if the battery is internal, then usually the mic's
phantom power requirements are on the low side typically since rather then attempt to derive 48volts from an internal battery, they simply use the lower
voltage. So in that case performance is probably about the same, but the down side is if the battery drains down at a critical time. SO in general I prefer using
phantom power
HOWEVER if your board only has global
phantom power, ie like the
mackie where there is
phantom power on all inputs or none, then depending on your inputs and requirements it might be better to have a mic which uses its own
phantom power, so that you do not have to feed phantom to devices you don't want to.
IF you are buying a mic, having an internal battery for a
condenser has the advantage of flexibility in being able to be used with a device that cannot provide it externally. THAT SAID, the better mics tend NOT to have a built in battery, for instance while the AKD C1000 does, the AKG C3000b does not, or the Studio Project family do not.
Now you can get an external
phantom power unit, the thing you need to watch for is that it really puts out a full 48 volts, some of them fudge a
bit (the ones for instance that may use 9 volt batteries or 3 nine volt batteries MAY not put out a full 48 volts instead can be 18 or 30 volts. For some mics this is not a problem but for others it can be.
So as always there are tradeoffs
Sharyn