All gaming dice I’ve seen have rounded corners. Casino dice have squared corners. Rounded corners lead to spinners that wont settle down for 10 or so seconds.
I use chessex dice. They look good. I have 10 or so matched sets of 12. I’ve played many games, rolled dice many times, and its hard to imagine a systematic roll bias on a d6 that isnt overcome by other factors. The only complaint I have here is that sometimes the pips are a similar noncontrasting color (green dice with yellow fill), and the fill is sometimes uneven so the roll is harder to see than black on white.
What is much worse, in my opinion, are the nonstandard die that have a national symbol or other symbol on them. This is sometimes on the 1, and sometimes on the 6, but either way, an unscrupulous player could represent that it was either. Some people play pretty fast and loose and one of the easiest ways to cheat is by misrepresenting what you rolled. Watch for people who sweep the dice up quickly, and whose methods change depending on whether you are watching them directly or not. Cheating and slopping are much bigger concerns than nonrandom, hard to see, or spinning dice, IMO.
A good rule of thumb is that anyone can roll any dice that you use. There are casino style dice made especially for cheating at street dice that contain only 1/6, 2/5 or 3/4, these are easy to add in or out and look exactly like the casino dice of that color.