This is one of our most frquently-asked questions. The MKII tone and performance is completely improved from an MKI.

Here is the list of things the MKII has that the MKI does not have:

London Power / Power Scaling control 12 watts down to less than a 1/2 watt
Custom Mercury Magnetics transformers w/ 4-8-16 ohm taps
SoZo vintage style mustard capacitors
Use EL34/KT66 /KT77/6550/6L6/5881/6V6 ECT
DC Filaments for ultra quiet operation
1/8″ aluminum chassis for the true vintage British amp sound
New improved 3 position rotary decade switch that alters the circuit for true 60-70-80 Marshall Style tones. (JTM 45 / Plexi / JCM 800)
Passive FX Loop