Which is to say, neither the Marx Brothers' best nor their worst, but the end of their great period and the beginning of their decline. MGM was simply a studio that (with few exceptions) didn't understand comedy. After this GO WEST has its moments, but THE BIG STORE is nearly a complete waste of time (and when I say "nearly" I'm being charitable --- offhand I can't thing of a single good thing to say about it).
AT THE CIRCUS, on the other, hand, still has many things to recommend it, if you have the iron will it takes to sit through the incredibly schmaltzy and irritating "love" angle. Lots of funny one liners, Harpo riding around on an ostrich and bopping people with his horn, the problematic "Swingali" number (which offends many people but somehow only makes me reflect that Harpo transcends racial barriers), a guy in a gorilla suit, and last but very, very far from least, "Lydia the Tattooed Lady".
For that number alone you should see this movie. Of course if you're a Marx fan you've seen it anyway --- you've probably even seen LOVE HAPPY.
Ugh.