Yes same pictures but very different layout.
https://en.wikipedia.org/wiki/Google_Photos
Google Photos is a photograph and video sharing and storage service by Google. It was announced in May 2015 and spun out from Google+, the company's social network.
https://en.wikipedia.org/wiki/Picasa_Web_Albums
Picasa Web Albums (PWA) is an image hosting and sharing web service from Google, often compared to Flickr and similar sites. The service links with Google's photo organizing desktop program Picasa.
Back to my original question...
Are you seriously quoting wiki to... heck I don't even know what exactly you're trying to do, really
I use Google's photo storage extensively (I don't really care what it's currently called or whatever new name Google decides to come up with), so I'm familiar with whatever methods to access it, including setting up the albums and some amateur post processing from the Picasa desktop app.
So, back to your question, I don't know if there's any actual drawback. 'Google Photos' (the name) is relatively new, and maybe people just aren't familiar with it. My family has been sharing pictures using Picasaweb with each other since even before Picasaweb was swallowed by Google+ (now it's been decoupled again), so we've always been using the same Google-based storage to share photos. The methods slightly change through the years, but it's all the same damn collection of photos.