I'm using pine straw rather than wood chips. Here in the southeastern US pine straw is free for the raking in my yard (or, if I should ever run out, in my SILs' yards), or inexpensive to buy.
I suppose the best litter for chickens is what you can get for free, or at a very low cost. Where I live, a small straw bale costs about $5.00. For $5.00 in gas money, I can get a trailer full of free wood chips.
Fresh straw is good, but I find that straw gets wet, moldy, and will smell bad. So when I used straw years ago, I was always cleaning it out and putting down fresh straw. If I got my straw for free, maybe that would have been OK. But like I said, we have to pay a pretty good price for a bale of straw where I live. When I found out about wood chips, and then found a free supply, I switched over to wood chips and never looked back. Like I said, I only clean out the wood chips maybe twice a year, compared to cleaning out straw every week. Wood chips just work out better for me, but I'd probably still be using straw if I got it for free and did not have free wood chips available.