Having your bearings outside the BB shell with exposes them to the elements far more than a sealed square taper BB unit. They are also not going to be easily replaced if you are traveling further afield than a well stocked LBS in a reasonable sized city in the first world.
If the bearings were open, then exposure to the elements might be a problem but all of the external bearings I've seen are very well sealed. Well enough that you can throw mud at them on a mountain bike and not worry about it.
Unless I am mistaken a Phils BB takes a special tool to install/service that you'd better carry with you if you want to deal with it on the road.
This is what the hub looks like after you use a single...okay maybe two
...5 mm allen wrenches on it
Absolutely no other tool is needed to
completely disassemble the hub.