Hi Carlo,
Firstly, I know nothing about the Shroom so cannot make any real experience comparisons.
I have made a few comments on the Starboard website on the new 7'10, link below at the bottom of the page.
sup.star-board.com/2019-products/2019-hypernut-foil/In the past I rode the smaller 7'2 HN as they tend to work better when the size is matched to rider weight. The downside of this is that in the smaller sizes they have no glide. The popularity of the larger sizes is that they maintained good glide but for a lighter weight rider they where a little harder to turn and engage the rail due to the rail width.
The 2019 versions in my opinion have addressed this by reducing the rail width and profile, making these board far easier to turn off the tail and the mid rail. The board does feel smaller than the 8'0 but there is no sacrifice in stability through the widened outline further forward and the flatter deck.
Also the new fin setup with the smaller rears makes the board a little more responsive and fun through the top turn, you can really push it on the rail and slide the tail out. It does take a little more practice upon entry into a wave as it can slip if too flat, but you just need to engage the rail sooner.
Even comparing the 7'10 to the older 7'8, I think the 7'10 is a better more responsive board. I found the 7'8 a little thick on the rail and the board wanted stay straight too long if the rail was not engaged. The new 7'10 is simply an easier board to ride and has improved performance for a lighter rider.
In Australia we are still selling a lot of Hypernuts where this style of board has lost traction. I think this is due to the relatively longer length and wider outline that Starboard maintained over the other brands. Glide is important for early wave entry and most people do not want to sacrifice this for performance.
Hope this helps some
Cheers,
Marco