There was actually a pretty good discussion including a poll done on a similar topic.
Besides this, I will chime in with my personal opinion. I am a binder collector and I collect raw cards only. My personal belief is that the premium that I have to pay for a graded card, I might as well use that money as funds for more purchases. I have only ever purchased 2 slabs. My first one was because I was not able to find any raw copies and the graded copy ended up being cheaper than the raw copy because the card just flew under the radar during the auction. It was a PSA 9 and I cracked it immediately. The current slab that I have is a PSA 8 and I got it only because the seller negotiated to a price which was lower than some raw copies of the same condition.
I think when it comes to graded slabs, it gives you a security in terms of card condition. A seller mentioning “Lightly Played” on a raw card is still subjective which might differ from your standards. However, a card graded 7, you can more or less know the condition with high confidence because it is supposed to adhere to the company grading standard.
I am very forgiving with the card condition for my binders, so I would always choose to stretch my money as much as possible and buy raw. So I will personally go for the 70 USD deal on the raw card and save 30 USD on the graded copy (in your example). But I know a lot of others who are happy to pay the 100 and get an assured conditioned card. Sorry for not directly answering your questions but I guess it depends on your priorities regarding card condition.
Cheers!