I've tried the plastic heart shaped and various other plastic clips.  For me. . . they are obnoxiously difficult.  So, I gave up on them.  These clips do the job well once you master the learning curve of use.  Per another reviewer hint. . .. I also slightly bent the center at the end at both sides of the fastener downward so that your strap can more easily slide in.  I also leave one side always attached to one strap so when I put on the bra, I only have to slip one side of the fastener to one strap.  Much quicker to take on & off that way.  I don't actually fasten the bra in the back until AFTER I have the 2nd strap clip attached.  Only after the strap clips are attached to both sides.  . . then I pull the bra down and fasten the actual bra in the back as I normally would.  At least this is the process that works for me.

I've tried almost every iteration of strap clips out there.  My favorite is still Bra Barrette.  Those were the quickest & easiest to use.  But, I can no longer find them anywhere.

These are the next best thins and they work !!  My straps do not fall down and the strap clips have never come unattached.  They are very comfortable. . . I don't even realize they are on.  I'm petite. .. so I have these straps on the tightest/shortest possible.  I wish they came one size smaller.  But, I wouldn't walk out the door without it.  Pulling up your bra straps constantly thru out the day is absolutely annoying.  Again, they are the easiest, most stable & comfortable strap clips that I can currently find on the market today.