hj is right. A toilet without a crack is better then a toilet with a crack.
We do however pull out a lot of the toilets that hj installs. They work for some, and not for others. Every once in a while we pull out Champion toilets, Cimarrons, Wellworths, Mansfield Alto, Briggs Vacuity, and I was at a church in Monroe that pinned warnings all over the bathroom about how to double flush the toilets that hj has in his home; the Eljer one-piece. That one works too. Just follow the directions pinned on the stall. Flush once, then use paper, then flush again. No worries mate! We keep the plunger handy in case you need it. But if you follow directions you should be good.
I think that 80% can use anything without worries. I thought I was in the group too, until I would visit my daughter, and dang if I wasn't having problems with her builder grade stuff. She suffered for almost two years before she "let" me replace them.
From the picture, I can't even see a crack though. I see adhesive around the bolt hole.