One place for them all. It is easy to find all apps for every platform. AppAgg is the application aggregator for the multiple platforms. This means that the webpage contains all the necessary information about the application, including place to download and price. Website is also surf-able and pleasant to search. Dark theme available.
Users can also signup with the email ( requires the mail confirmation) and save preferred apps in the lists. Confirmation email arrives within seconds, there is no complication around the login or captcha.
Once created, you can set alarms in the list to notify you about the discounts, or you can subscribe to other people lists ( RSS feed available). The website has also a basic profile page, user image is Gravatar.
AppAgg has a repository on Github and account on the Twitter. It can't be really compared, because the two serve different purposes, but AppAgg is similar to Alternativeto.Net but in my opinion much better, especially visually.
All additional app/game information are available, plus you can write or read reviews. Some developers/brands pay their way up to the top on the major app platforms, so it is advisable before placing your trust into anything or anybody, to visit a few alternative places like the AppAgg that offer the unbiased opinions.
Website also offers the invitations, for you to invite your friends and peers to check up a website or for you to put on your pages or blogs if you like.