I always try and put everything inside my pack. I have a Black Diamond/Bibler tent which is very small so getting into a medium sized lightweight pack is no problem. I usually split the tent parts with whoever I'm with if I have a tent mate. My main summer tent has no poles so it makes things easier - I use trek poles. If my pack is pretty full with no sagging I will put my sleep pad into a side pocket. This is easy for me to do b/c I have both a 3/4 Thermarest and a Big Agnes full which roll up very small and compact. All my packs have stretch mesh side pockets so that's usually where I always put my sleep pad and water filter. Easy access while on the trail. If I'm tired and want to sit on something besides a rock, I can grab my pad and then use my Thermarest camp chair with it. If my pack is not quite full and I need more support, then I take my sleep pad out of its stuff sack, fold it and put it against my back. My packs have no frame support so sometimes this is necessary when no completely full. Either that or I have to keep my Platypus full until I reach camp.

Winter is a different story because I use more gear, but I will take a heavier duty pack with more volume and still try and get everything inside.

I personlly don't like lashing things onto the outside of my pack unless it's a cup or something. I have greater peace of mind knowing I'm not losing anything or puncturing something. I have pack rain covers for all my packs so that keeps things dry in case of rain for the things like my sleep pad that are outside my pack.