I'd say it depends. It certainly has its strengths, and I have definitively encountered (image) searches where Bing's results where noticeably superior to Google's, but one area where for me Google shines and Bing fails is the ability to search for "site:example.com keyword" and as long as the search keyword in question is recognised by Google's image recognition pipeline, it'll return search results not just based on the classic "index nearby text and hope it's somehow related to the pictures" method, but also based on the actual image contents themselves.

With Bing either they don't do that kind of image recognition at all, or maybe it just doesn't work as well in conjunction with the site:-operator, or maybe its image recognition simply has a much more limited vocabulary as compared to Google (at least for the things I'm interested in) – in any case that kind of search for me simply works much better with Google.