They're different types of players. Rabiot is a better presser for sure. I'd personally take Tielemans for actually progressing the ball and creating chances. Rabiot had a decent season at Juve but he also had a lot of poor performances for them before this season. Some of that is down to him being used in so many different midfield roles during that time, but he's not an elite midfielder. I think some might be being influenced by his good performances at the World Cup. I'd personally always take Tielemans of 2 years ago ahead of Rabiot. Tielemans is still only 26, so there's not any real reason to think he couldn't get back to that level in a team that's actually functioning well, which Leicester certainly haven't been this season. Getting both on frees seems like a logical decision. I didn't suggest Tielemans as an alternative, if you actually look at my post I included both.