Off the top of my head -
Placement of the turbo. Which equates to:
Cleaner/simpler install with more of an OEM look
shorter length of the header pipework
(Turbo dependent) faster spooling and less lag
lower centre of gravity
lighter system
Shorter oil/water feeds/returns
less hot exhaust pipe near the belts
less heat soak and better air flow as the turbo isn’t wedged up between the top of the engine and the bonnet
I’ve been buying on/off from Fensport for about 20 years, so if they use the AVO kit then I trust their knowledge/experience/opinion.
AVO’s kit is really well designed and built. I’ve seen/heard of quality issues on a number of other kits.
Lots of US tuners are also using the AVO kit and making lots of reliable power.
I only chose to go SC only as I thought the limited supplies of the Cosworth package along with their huge development/testing process (plus their name and reputation) meant it would retain more future value and in 20-30 years may even go up in value.