Is a new engine merely a remanned engine? If not what are the pros and cons?

 

I believe there are actual guidelines to the terms that businesses can use, but I don't feel like digging through the Uniform Commecial Code to see if I'm right
IMO this is how the terms breakdown:
NEW: means NEW as in never been used. Sometimes you will see it referred to as NOS (New Old Stock). If you can find this sort of engine it would be nice. Probably pretty pricey, but nice. The only concern would be it's age and how well it was stored. Wouldn't be much good if it sat around and dry rotted gaskets or cylinders were left open to the environment and got rusty.
Remanufactured: requires the actual breakdown and machining/repair/replacement of all internals. If you come across a place that says their engines are remans and when asked say something like, "the pistons looked ok so we left them in.." run away!
Rebuilt: whatever was broken or damaged was repaired sufficient to get the unit functional again. Definitely the bottom of the barrel in quality and price and you get what you pay for.
Just an opinion. Others may vary.

 

What engine?

 

3.4 from a '96 4Runner.

 

F451 got it.
New means new. Not hard to grasp that one.
Reman generally means all major wear components that can wear or age are replaced and the rest is tested for spec and remachined etc. Pretty extensive and the result is theoretically as good as a new engine. With some shops it's better than new because they might take more care (matching up pistons etc.)
Rebuilt is typically supposed to mean new pistons, rings, main cam and rod bearings, all gaskets, freeze plugs, and oil pump, and reuse the rest if it looks good. But it can mean anything from "we put in a good used head gasket and replaced that bent valve" to one o-ring short of full reman. Crap shoot unless you know the shop.

 

The new engine is pure Toyota manufacturing.

The rebuilt engine is built by someone else.

Go with the Toy. They're good for about 250,000 miles. The other one is good for an unknown number of miles.