So Palace has more cups than Arsenal in the last 5+ years or so. These type of things matters, while it is not a long term thing and maybe we would be right to say that Arsenal is better team than Palace. But it is important to note that Palace won while being a worse team, what more can you do?
Crystal palace also has more trophies than Manchester city in the last one season. I am not an Arsenal fan but I think they have just been very unlucky recently. They have actually played well and they deserve to at least win something but football can be unfair sometimes especially when you aren't consistent all season long as Arsenal has been.