To make a 4-foot wide table, primarily out of oak or maple, is it better to glue 2 or 3 pieces together of 1 ½ to 2 ½ inch thick wood, or is it better to have a special saw to cut a 4’ wide solid slab?

Which one will not cup or twist over a long period of time?

Also, which is better…..air drying wood for 10 years or kiln drying?

Lumber in general will cup some, but some more than others.
Kiln dry or air dry will not be a big difference. I've seen more issue with drying at a high temp.
Even if you air dry, it is a good idea to "finish" the drying in a kiln for a few days. Air drying in Indiana rarely gets the MC below 12%. Ideally you want it to 6% to 8% range, then allow the lumber to acclimate back to 12% before using the lumber.
The wider the board the more problem there is even if just a small amount of cupping, since you would plane a lot of lumber away to get it flat.
One method is to cut the board wide and dry it that way then before planing it. Cut it into boards 6 to 8 inches wide. Plane and joint these. If you line up the grain well when you glue it up, it will take a trained eye to see what you did.

My sawmill can cut up to 24 inch wide slabs from an up to 36 inch diameter log. I cut 2 slabs back to back and create a bookmatched surface when the 2 slabs are glued together.

Let’s say you have a 12” wide
Icee with 1” of cup. If you cut this in half to get two 6” wide pieces, you will have 1/4” of cup. Rip again into 3” widths and each piece will have 1/16” cup. Of course, the side will not be a perfect 90 degrees to the face, so it will be necessary to re-machine the edges. Then glue the pieces back together. If glued in the same order as they were ripped, the grain will come close to matching. However, usually the 3” strips are random to give grain variation.

Air drying for ten years has a high risk of insect damage. Properly done kiln drying eliminates that risk. In either case, poor storage after drying can result in insect damage.

For a table that you want to have a flat surface after manufacturing, it is necessary to control the Final moisture content. Wood will not cup without having a MC change. As most homes and affixes have a wintertime humidity that results in about 6% MC, so, we target 6.8% MC target. In most parts of the US and Canada, air drying can achieve a low of 13% MC even after ten years. So, before use, the wood needs to be dried further...in a kiln, warm room, etc.

Both have given you excellent advice/info. I saw wide and dry wide....THE MAIN issue I commonly see with either is IMPROPER joinery. IF you start with a MC close to the final area it's to be used at then there won't be a big MC swing BUT you still will have a movement. Wood is alive whether standing in the woods or laying as a table, it still breathes, moves, FLEXES it's muscle IF contained (improperly jointed). A solid one piece top has it's issues JUST as a glued up top. it's the final desire and/or look you seek to achieve.

THE #1 issue I see with table tops cupping is restricting the large surface's movement.
#1) DO NOT glue ANY joints cross grained.
#2) Allow for top to "float/move" on the under base via slots, enlongated holes, pins, sliders, etc.
#3) DO NOT full glue a bread board end IF chose to go that style. It also has to float as that is crossgrain directioned wood. A true breadboard end will ALWAYS have a edge difference as MC changes move the main top width.

Look at my website link (sorry, I haven't put new content on in a while). I've also changed saws to Cooks Superwide 54".
Enjoy your build. I suggest getting correct info on top joinery prior building as most I end up advising is after the fact and have a mess that lose that beautiful slab that's one of a kind by improper joinery and top cupped too bad or busted with stress/tension cracks.

Where do you source 4' wide slabs?

hearne hardwoods in penn. they have a 67in throat bansaw

It is important to remember that wood only moves in response to changes in MC, or change in the relative humidity in which it lives.

The wood, once jointed and planed will be stable. There is no reason to expect movement unless you are aware of moisture problems.

David, I've heard of VERY few places that DON'T have a MC/RH change from season to season.
BUT that being said ,EVEN if you may be the lucky one to be in one of those places, ALWAYS correctly build expecting movement and you NEVER have those worries or issues of the wood flexing it's muscle....who knows, you may sell it or an heir inherits it that live in a different Climate/MC part of the area/world. I wouldn't want a future owner being dis gruntled over a MC change.

Get a copy of "Understanding Wood" by Bruce Hoadley. It is a great resource for anyone wanting to work with wood as opposed to against it.