I like the Moto charger- I keep it in my laptop bag because it's portable. However, I use my BB chargers primarily. You're more likely to blow up an underrated charger than harm the device in most cases but Blackberries don't exactly sip power...
If its micro usb, shouldn't all of that be the same?
The voltage should be in spec, but the current rating may be low. With my Storm I couldn't charge with my wife's car charger when I was streaming music with the screen on- it's possible that a low end Blackberry charger won't put out enough juice to charge efficiently but it's unlikely to kill anything. Then again, if something does go wrong it's finger pointing between a faulty phone or faulty charger so there's more headache.
a PC's USB port is usually spec'd to put out 5v and 500ma.
Chargers I have from my older blackberries, motorola phones, and smart phones which have a USB end on them have 5v output, but 500, 550, 750, 850 and 1000 ma. The higher ma rated chargers do charge my devices faster.
So far, I've been using the same chargers with all my phones since 2007... it hasn't hurt one of my phones yet.
For the phones that have MicroUSB ports on them, I use the Moto SKN6252A adapters, and still continue to use my older chargers at my desk.
I'v done this with my Moto Razrs (v3c and V9M), Moto Q9m, Blackberries (too many to list), HTC VX6900, Moto Droid, Moto Devour, HTC Inc, etc.
ADD: The wall chargers I use today are a mix of Blackberry and Moto chargers that supply 750mA or higher, still use the MiniB to MicroUSB adapters, and I've not had a problem yet.