You didn't mention the year. The V8 had slighltly more power in 2005. One thing to know, the V8 has a timing belt and it should be changed at, you guessed it 90,000 miles. Since the engine is a interference engine, should it break, major damage can happen. I bet you 10 to 1 that the belt has not been replaced. So, add that exspense to your price.
We have had a bunch of V8 vs. V6 threads and sometimes had to closed them down, some members get a little out spoken for each one. The V8 is considered a very good engine, the mileage suffers a little, but not as much as you would think, maybe 1 or 2 MPG. They are known to last and last. They are smooth and can tow more.
Two more things to keep in mind, if you are looking at a 4 wheel drive on the V8, it is full time full wheel drive. Not a bad thing, just keep that in mind. Second, if you are looking at a 2004 or 2003, the V6 came with a 4 speed and the V8 came with a 5 speed. In 2005 all 4Runners had 5 speed automatic transmissions. So, the V8 will have a 5 speed.