#1
I recently purchased a Ted Weber Load Dump for my Peavey Classic 30. I love the way it sounds; my amp is now much more versatile. I'm able to get incredible tube breakup at reasonable volumes. The tone does suffer somewhat when I bring it down to bedroom levels, but I still prefer the attenuated saturated tone to the non-attenuated tone for night time practice.

I chose the resistor based model because of the price. How much am I missing out on by not going with a speaker motor model? Has anybody tried both? Was the difference that noticeable?
#2
Well... a speaker is a reactive load, so it's impedance changes based on the signal you're putting on it and those impedance changes affects the way the amp reacts so there is this constant interplay between the amp the speaker. With a resistor based attenuator, you don't get that behavior.