Of course there is a difference. One is completely hand made and one isn't. one is manufactured and one is podshaved.
Laver bats are impeccable in their finish and you will struggle to find a similar bat finish anywhere.
B3 is a totally new philosophy about you being able to design your bat using a test player bat designer to guide you.
Wood supplier is the same. Crown is low density. Signatures are aesthetically outstanding according to Lavers page and some of the posts.
Press is similar although I think lavers take longer to get going. Both go at that quality Willow.
One is 440 US cheaper. I assume this is with the 25% off voucher?
http://voucher.b3cricketusa.com/You could buy a almost identical profile and weight training B3 bat in grade 2, both knocked by B3, B3 pads, couple of pairs of B3 gloves etc with that change. Ask to see the cleft pics beforehand and have bespoke season with streaky. Then when the bat needs replacing you just order the same bat.
It's head vs heart mate.