Should I get a rock shox recon silver tk 26" solo air or the same thing in coil?
The advantages of a metal spring are simplicity, reliability and feel. Not much to go wrong with a spring and not much maintenance needed. They also tend to feel more linear but air forks are not that bad these days.
Main downsides are weight and limited adjustment. Most forks at the lower end seem to come with springs that suit someone on the lighter side of average, probably because most bikes are bought by/for teenagers, So if you are a lot lighter or heavier then you won't be getting the best out of the fork. Lighter and stiffer springs are available but they're not cheap so few people buy them.
An air fork is lighter and lets you adjust the spring to do pretty much exactly what you want by altering the air pressure. In my opinion this one feature is worth the trade over a coil.
They tend to be surprisingly reliable but do need the odd service to keep them that way. All forks need serviced but air ones have extra stuff to do.
The lockout on a fork is a feature of the damper so, all else being equal, will be the same on either a coil or air fork. Similarly, rebound is a separate feature that has little to do with the type of spring. The better the fork, the better the rebound will be, irrespective of the type of spring.
For general cross country, I'd go for an air fork any day.