Another vote for Rokstraps. One of those things that:
A) Initially look expensive (for what they are).
B) Don't seem worth getting; I mean, I'm fine with my current straps, right?
C) Once you've tried them, you'll never go back to using other straps.
Main advantages are: You don't need to adjust/retension or keep checking them. You just secure them and then can trust they will stay done up. You need one, two tops, to secure most things and fitting takes seconds. No need for an intricate 'weave' of knots of the loose ends to stop it working undone in transit.
I've carried an 8ft Christmas tree on my bike with a pair of them. I carry well over a grand's worth of mountain bikes with one Rok strap on my car's cycle carrier; that's how much faith I now have in them.
The only time I take a different kind of strap these days, is as Maggot says, when I'm taking a ratchet strap along anyway for some other purpose (tow line, for tying the bike down on ferries, etc.) and can use that for what I would normally use the rok strap for.
I like my bike because I can overtake 4x4s down farm tracks with a week's worth of shopping on the back.