I'm sure it could be argued, but in my experience a5e characters are more powerful than 5e characters if you exclude broken builds and overpowered design.
Overall character options are better-designed, and the characters have a lot more "cool stuff;" sometimes too much to keep track of for new players, but once you get used to it it's great. The origins (heritage, culture, background, destiny) can give a character a lot of power.. heritage can provide one damage resistance, and culture another.
That isn't to say that a5e character options don't have their own flaws- I'm building a doc of house-rules to deal with things that have proven to be problematic. But feats, spells, magic items, etc. are so much better to deal with as a GM, and obvious pains have been fixed.
That said, at first glance players might dislike changes. For example:
Paladin players will see that they're no longer smite-machines because the a5e version (herald) is designed in the spirit of older paladins, where smite evil is one piece of the toolbox but not the class' entire identity.
On the other hand, they basically just made bards and berserkers(barbarians) better; and they were already good in 5e.
