I think it depends, if you are looking to resell them then yea getting higher end cards signed can devalue them, however if you are an IP sig collector, then getting the higher end stuff signed gives the card more value to you and maybe other IP collectors. But if its for your collection, it really comes down to what you like.
Personally I dont like IPs at all, but I can definitely see the draw in collecting them, the guy on this forum that has the cameron smith and JT collection, with just about every card signed is an amazing collection and I genuinely appreciate his interest in getting that done and have to say it looks amazing, its just not something I would personally collect.
So I guess it depends on your own tastes. If I was collecting IPs, I would definitely want a non-IP version as well, but like I said, it comes down to personal preference.