You'll hear arguments both ways. The poly spacers have been said to compress over time and you'll loose some lift, but I don't know that this has been proven (or at least to a considerable amount). With the aluminum spacers, they say you'll get more noise. I had the 1" Toytec aluminum spacer and never noticed any at all. Personally, I'd choose a spacer based on price and lift amount. The Cornfed will give you 1" of lift. The Daystar is commonly mis-advertised, it will give you close to 2". I'm not 100%, but I think the 1" and 1.25" kit are the same.
It is important to note that on the 4runner suspension, you will get double the lift as the spacer thickness. A 1" spacer gives 2" lift. Some get this wrong. Cornfed has it right, their spacer is 1/2" thick, gives 1" lift. Toytec is close, their spacer that is listed to give 3/4" is actually 1/2" thick and gives 1" lift. Daystar is way off, they list spacer thickness, so expect ~ double that.
Now that the basics are out of the way, my personal opinion (and plenty here will agree) is to go with a set of OEM springs off of a 07-09 FJ Cruiser in addition to one of the Toytec spacers. Which spacer thickness you need (1/4" or 1/2" thick) depends on your 4runner (v6 or v8 and 2wd or 4wd). This setup not only levels the 4runner, it also results in a much improved ride. Most FJ guys sell their suspension for a reasonable price when they go aftermarket. Craigslist or the
FJ Cruiser Forums is a good place to look for the OEM FJ coils (used).
Check the links in my sig for more info on the above mentioned setup.