I grew up using Ernie Ball 9's and I was relatively happy with how they felt and played. It was actually until I found Thomann that I even realized there was such a thing as 8's and even 7's. It completely changed the way I feel about guitar for the better.
The Ernie Ball Extra Slinky set is fantastic in many ways. I'd say the difference between it and 9's is probably more pronounced than the difference between 9's and 10's, in part because of the 3rd strings being a 14 instead of a 16 or 17. The 2nd string being an 11 keeps the tension right. I've tried other brands such as D'addario that use a 10 in their set of 8's and the whole thing was uneven - the second thinnest string would bend way too much compared to the first and third and even it chords it felt out of place. Their 15 instead of their 14 also took away from the bendy quality that pretty much is the whole point of playing 8's. Ernie Ball provides a much better and much more consistent gauge for these extra thin strings. They sound great when new and still pretty okay even after a ridiculous amount of usage - and most importantly, they somehow stay in tune remarkably well once worn out. I once tried a set of GHS 8's and after one week, I had to tune my guitar every 3 minutes. Maybe my package just slipped under GHS's quality control somehow, but I grew up with very little string money so I had to make my strings last. Ernie Ball's Extra Slinky offer everything you can expect from inexpensive nickel-plated steel strings - a good lifespan, good intonation, good tension throughout and great packaging,
Ultimately, string-gauge is subjective just like brands are. I had no particular loyalty to Ernie Ball and ventured into many other brands, only to find out that what I wasn't noticing was exactly what makes this brand and this product excellent: I took it for granted that all 8's would feel thin in a balanced way, that they'd stay in tune longer than they had any right to and that they'd sound this good for this price. I was wrong. Ernie Ball's 8's are the perfect set for players with a light touch like me who don't really click with anything else for standard tuning.