L0 and L1 means 2010 and 2011 model
the L prefix denotes decade eg 2010- 2019
then the number denotes the year within the decade.
All K2-K9 + L0-L1 bikes are the old shape
L2-L4 will be new 'Glee' model
as for differences- there is no difference between those years, but different spec options like:
X - Non ABS but came with hand guards, bash plate and engine bars
A - ABS but no other options unless buyer paid for them each.
GT - ABS, full luggage, heated grips, hand guards, engine bars and bashplate.
EXP - as GT but with aluminium panniers and no top box.
Different luggage racks came with different models- boxes will not interchange on the various racks.
NB- some believe they have an L1 on the new curvy 'Glee' DL650- as some bikes were sold in 2011 but were all 2012 models so should all be L2 but dealers have been known to get the registration wrong.