In reality you are going to get very little from an upgrade. The Honwaves are great boats (I've had 3) so I will try and give you a direct comparison.
Tubes will be a bit bigger, this combined with the V airdeck will give you a dryer ride. The V hull gives slightly better handling but you will be hard pushed to tell. The 2.7m Honwave will feel safer (because the floor is deeper) but has slightly less useable floor area (The raised bow means anything you put at the front rolls back down the boat).
Performance of the Honwave will be similar, it will get on the plane with your 5hp and 1 person, might even get on with the plane with 2 lightweights on board.
Having said all that, most of us just buy another boat cos we fancy something shiny and new
. The Honwave is a great boat and worth the money, you will also get good money for your current Avon so the price to swap wont be huge.