any reason why the dished are better?

Dished pistons were for low compresion engines, generally Type 2s so they could run on crappy 2** petrol.

What cc's your engine at the moment?

far as i know its a standard type 3, so 1584cc

They do flat and dished top pistons for high and low compression as David says. A new quality set is fit and forget.

Well worst case scenario it'll be about £250 for a set of 4 new pistons and barrels. These being some forged ones, not the cheapest of the cheap as I want it to last.
Hopefully no valves etc have been bent or crushed to add to the total..When I was on the phone to the mechanic first thing he said was "ho hoo, gonna be expensive!" Wonder what his rates are haha. Oh well... I guess its something that has to be done. No real escape from it unless I want a very large yellow ornament in the garage.

  haha! He was also adamant that I make sure all the tin wares on etc, I have it all but nothing on the bottom of the cylinders, as it was "committing motoring suicide without them"

Going down monday, so best bring me cheque book!

any reason why the dished are better?

Dished pistons were for low compresion engines, generally Type 2s so they could run on crappy 2** petrol.

What cc's your engine at the moment?

Just about every aircooled VW engine is capable of running on 2* fuel, it is simply a matter of adjusting the timing, they were designed to run on the worst fuel available in Nazi Germany. The original Type 1 engine design specification was to be capable of transporting 2 adults and 3 children at 62mph, whilst using averaging no less than 39mpg. I am however not disagreeing with the low compression part. All of the aircooled engines that followed were simply variations on a theme that slowly produced greater levels of horsepower largely through increases in engine displacement.

Low compression engines may be more preferable for use as generators as low compression leads to longer life, lower heat output, lower cost of construction and greater reliability, at the cost of performance and efficiency. A higher compression engine  with the same parts will also have a tendency towards pre-ignition/engine 'knock"/"pinging" due to an undesirable burn pattern caused by excessive heat, this is often counteracted to a degree (pun intended) by changing the timing.