In my college days I worked in an engineering test lab. Consumers Reports was our bible for both their product tests and methods of testing products. They keep statistics on repairs of all cars. For example, a Toyo Camry will require 50% less repairs than the average new car will. This is both for 4 and 6 cylinder engines and assumes all proper maintenance is done. So both engines are reliable. Photocopy the maintenance required that's in your manual in the glove box and you will be fine.
In my limited experience fixing my own cars, the 4 cylinder ones are much easier to work on and cheaper to fix. The spark plugs are in a straight line, while the v6's are hard to get to on the back row sometimes. Also, everything is crammed into tight space on the V6's when replacing alternators, AC compressors, etc. On my 24 valve 2003 Taurus, they had to take out the radiator and many other parts to replace the AC comptressor; ditto for the alternator. And those will have to be replaced, usually before 200,000 miles, at least for an American or European car.
A friend of mine has an old Toyo Camry Stationwagon with 275,000 miles 4 cylinder with the original engine still running good. He uses synthetic oil. I'm not sure if that matters or not. If you google "Consumers Reports The Surprising truth about motor oil, they have a great study they did. It was done in 1996, but is still great article.
The other gentleman's post about all the fluid changes he does was great, but will cost a lot if you pay to have it done, especially at the dealer. I would back off that schedule to what my manufacturer says in the book in the glove box and not what the dealer says. My antifreeze and brake fluid look like new in my 2006 Toyota Avalon, as clear as honey after 85,000 miles and 10 years old. The book says to change at 5 years or 120,000 miles, but I go by mileage and appearance, as do several of my mechanic friends. The last time I went for an oil change and inspection at my Toyota dealer, they wanted to do $1200 for changing these fluids that look like new and replacing an axle that leaks a few drops of oil and flushing the engine, which is bad for it, and cleaning the fuel injectors and carbon in the engine. This car runs absolutely like new. I told them I didn't have the money right now, that I always pay cash, and would come back when I saved up the money. Well, I still don't have the money saved up for that for some strange reason.