The Peterson Guide is still a great guide, and compact.
I use in the field NG and as standby Eastern Sibley.
Another vote for National Geo.
Especially if you can get a used "old one";......I think the paintings have more depth, and truer colours, than any other N. A. guide.
Sibley for me--little one in the field and big one at home. All the birds in the same pose for easy comparison, and every surface of every bird is shown. Try to find out what the underside of the wing of a tricolored heron looks like (which is actually an important field mark) from looking at Nat Geo--it's not depicted or described, but is easily found in Sibley.
Best,
Jim
Not sure why you prefer the old ones. Do you think the printing was better on those? That did happen on some European "Peterson" editions. But the newest NG edition is certainly larger and thus less convenient to use in the field. Plus, they changed to the so called new system as discussed in another thread some time ago. Also not particularly field friendly during the transition period.