6th edition Slann were unstoppable. Immune to miscast, drain magic from the enemy, etc... Pretty big difference in this edition.
Oldbloods, Scar-Vets, Saurus, and Cold One Cavalry didn't change. Similar prices and everything, IIRC. I think TG got cheaper in 7th. Saurus could swap between Spears and HW freely.
Skinks could freely swap between Javs and Pipes. 1 point per model to upgrade to Scouts (and still be core!)
You could also field a Southlands list and have Horned One Riders, which were Skink Fast Cavalry. Even had a special character for them. And the Southlands lists could take bows on the Skinks to accommodate the millions of 5th edition Skinks that are still in existence.
Kroxigor couldn't join Skinks but they could charge THROUGH Skink screens. Made for some interesting tactics.
No Engine of the Gods until the Lustria Campaign came out. Even then it was just a magical catapult, more or less. A misfire would kill the whole model.
No Razordons or Ancient Stegs.
Magic items were more or less the same. Same names anyway. I believe the Cupped Hands had an entirely different ability.
And we had sacred spawnings...
The 7th edition book definitely brought some changes. The 6th edition book is a good read. The 5th edition book is radically different.