According to the Wikipedia article comparing all Canon EF-D 18-55mm version the STM version has (in addition to the new STM motor) a new optical design (13 elements in 11 groups vs. 11 elements in 9 groups), internal focusing and an extra diaphragm blade (7 vs. 6)

So, the EF-S 18-55mm IS STM is not just the EF-S 18-55mm IS II with the new motor but a completely new lens that seams to be slightly better than the old design in every way.

Even if you don't need the advantage of the STM motor for video I see no reason to buy the older version (unless it's cheaper), I also don't see a compelling reason to upgrade for someone that already has the IS II but the new STM version is better.

BTW, you can usually buy seconds hand kit lenses for next to nothing because a lot of people want to get rid of them when they upgrade, a quick look on eBay shows that the EF-S 18-55mm IS II has been sold for as little as $40

According to the Wikipedia article comparing all Canon EF-S 18-55mm version the STM version has (in addition to the new STM motor) a new optical design (13 elements in 11 groups vs. 11 elements in 9 groups), internal focusing and an extra diaphragm blade (7 vs. 6)

So, the EF-S 18-55mm IS STM is not just the EF-S 18-55mm IS II with the new motor but a completely new lens that seams to be slightly better than the old design in every way.

Even if you don't need the advantage of the STM motor for video I see no reason to buy the older version (unless it's cheaper), I also don't see a compelling reason to upgrade for someone that already has the IS II but the new STM version is better.

BTW, you can usually buy seconds hand kit lenses for next to nothing because a lot of people want to get rid of them when they upgrade, a quick look on eBay shows that the EF-S 18-55mm IS II has been sold for as little as $40