I take a spare tube (or two) and some glueless patches as a back-up.
I do also have Slime tubes on my bike though and ride on Schwalbe Marathons and up to now the Slime tubes have done their job each of the 3 times I've punctured and stayed inflated and got me home.
Another vote for both. Except I use normal patches and rubber solution. It doesn't weigh much so not worth worrying about.
What IS worth worrying about is if you rely on a tube only, puncture 30 miles from home and don't notice the small thorn in your tyre left over after you change your tube after a puncture. If you have no repair kit you are then goosed.
Both. Carry two tubes and a pack of Park super patches. And glad I had them last weekend. One puncture on the front and three on the back. Swearing blue murder by the last one (which came half way up the climb from Butler's Cross to Chequers). Michelin Pro Race going a bit thin and passed their 'use by' stage. Should have replaced them weeks ago, so my own fault really.