I,m 90 something (a bit afraid of the wheigtscale as it will probabbly suggest it will be close to 95

) and paddled both.I liked the Naish8.8 and the high rocker feels secure, but imo the AB is more stable and the better surfing board but i,m biased as I own a AB8.8
What is important with the AB is that you really really need you to step back on the tailpad, that is where the action button sits and make you turn tight and accelerate at the same time. If you know forom yourself that you don,t move that much away from the middle, the Naish might be easier for you to steer from the centre...but from the back the AB8.8 is a true winner. But....unless you paddle on a very slow wave and choppy spot and need to paddle 25min+ to your spot...I would go smaller.When i,m trained i,m 90kg, now with winterfur and a 5mm hooded suit and 6mm boots and gloves the Starboard 8.5 Pro still floats me fine and let me catch with ease slow waisthigh face waves up to leash snapping decent swell.If you wanna be safe you take the 9.0Pro.
The 9.0 paddles faster as the wider boards because it is pushing less water as ANY X/Wide board simply because its 29 instead of 31.5/32 wide... and is supringly stable once you get the feel for it. An intermediate friend of me of your weight with a Mana9.5 could paddle it straight away in wind and lots of chop and Northsea chaos (conditions most of you guys not even considdering supping) and did catch waves with it within 15minutes.It took him a few minutes to adjust to the less volume and width, but once he got it he was shocked how much better it did surf and was still able to paddle easily on it.I got my 9.0 replaced under waranty and instead of the 9.0 I have now the AB8.8 and the 8.5 Pro.Those look close together but they are completely different boards. In slower and smaller waves or chop I grab the AB, when its cleaner, bigger, faster its time for the 8.5. Together they work for me like a charm.
When I need to go back to one board for just everything...I would go back to the 9.0 because its a bit less stable as the AB, but still pretty good in slower (logboard style) waves and not as nimble as the 8.5 on a good day, but not that far away of it either.Hope it helps