The rope kit is the only way to go. Low cost. You can buy them anywhere and they work. The rope will actually vulcanize with the tire and allow you to run the tire until it's worn out.
The rubber plug kit is a proprietary POS, IMO. You pay way to much for the tool. It's a complicated POS and you can't buy refills at the local Wal-Mart of part store. They leak if the hole isn't the perfect size.
I've used two and 3 rope plugs on big holes to get me home. Try that with a rubber plug.
Don't waste your money on that
It's a gimmick and a piss poor one to boot.