I prefer Chelsea
But on a serious note, I think some of us Chelsea fans worldwide do not feel rivalry with Spurs in the same way like fans from London. I look at Spurs and Arsenal like Everton and Leicester. Completely irrelevant clubs.
We fought for trophies with United, City mostly last 15 years or so. I mean we are 3 most successful PL sides in this period. Many games against Liverpool in CL as well. So they are biggest rivals for me, but ofc I understand that Arse and Spurs are probably bigger rivals because they are from the same city and I would feel the same way if I live in London and being surrender with them...