When buying a couch, comfort, of course, should be your primary concern. I recommend going to furniture stores and trying out each one that catches your eye.
This one is especially important to me, as I enjoy lounging on my sofa. You may find after sitting on the couch for a half hour your neck gets sore, so I personally recommend seeking one with cushioning for head support. If you’re like me, you’ll also be heading straight for the recliners!
I recently purchased a loveseat with quite a bit of back support, and it’s my only complaint about it. There is so much cushioning that it actually pushes out my back, which gets uncomfortable after a while. From now on, odd as it sounds, I will avoid seating with back support.
This is entirely personal preference. Leather is good because it is spill resistant and will last a long time (bonded and polyurethane will be less durable), but it can also be cold or even stick to your skin on hot days. It also requires cleaning to stop mold on other pathogens. Cloth, on the other hand, is susceptible to spills and is not smooth. Like I said, this is all personal preference.
My strategy, when it comes to price, is to find the optimal piece of furniture first and then focus on finding the best price for that piece locally and online. If you in absolute need of a couch now, price is more of a concern, but, if you are simply upgrading, I would recommend the former strategy.