Hi Dez,
I can't remember the percentage difference between the 10 and 12, its not as much if it were from 8 to 12. I'm sure someone will advise you on the stats.
I read it somewhere in the forum that if you go down the 12" LB path, the deluxe comes with a standard crayford focuser, which in itself is a very good focuser. However if you ask them to upgrade it to a 10:1 crayford focuser, you only need to pay the price difference, which is ~ $25. Worth spending as opposed to deciding to do a separate upgrade down the track, which will set you back ~ $100. Some some food for thought!
The 10:1 crayford gives you the ability to perform finer focusing. Seems a lot of people have gone this way over time.