The Pitzen Knot is a very strong knot for attaching fly to tippet. I find it is easier to tie if I hold the fly in my right hand to start( I am right handed). The davy knot is a simple tie. I start this knot by holding the fly in my right hand. Every other tippet to fly knot I start holding the fly in my left hand( go figure)
I personally think it is hard to beat the blood knot for a mid leader connections. For warm water I have been using figure eight knots on 3 piece leaders( butt- mid- tippet) The steps down from the butt are too big for a blood knot. You could also use surgeon knots for mid leader connections
One comment about relative knot strenghts.One study found out there was a 40% varience in in knot strenght among people tying the same knot. In other words find a few knots that are easy for you to tie well and are strong for your fishing application and stick with them