I have a piece of 12 inch square porcelain tile that I need to cut notch out of one side to fit around doorway. Notch is about 1/3 way down one side and is 4 inches wide by 2 inch deep towards center of tile. I've read where you can use oscillating tool,snap cutter, angle grinder, tile cutter, or tile saw. However, they all seem to have disadvantages- oscillating tool( very,very slow) snap cutter ( chance of breaking tile), angle grinder (very dusty), tile cutter (hard to make this type cut), and tile saw( cost). Is tile saw really best option?
How are you cutting all the other tiles? If I'm picturing this correctly you can't use a snap cutter for that type of cut. If you going to purchase something for one cut I would get a handheld 4" tile saw ($50 - $80). Because the blade is 4" you can carefully do the 4" wide cut without going too wide. You can also use water with it to cut down on the dust, trying to keep it wet may require a helper though. Another option is to have the home improvement store do the two straight cuts and then make the 4" cut with a dremel tool with a diamond blade, that will go rather slow but you can get a cheap one with blades for less than $20.
For a one-off like this, an angle grinder with a diamond wheel is ideal. Yes, it's dusty. Go outside and downwind. If you don't own one, someone you know does. Spend $11 on a diamond wheel if necessary and give it to the tool's owner as compensation. (I've used the 7" variant of that exact blade to cut hundreds of heavy brick pavers.) Use ear and eye protection. Don't breathe the dust--a breeze or a fan help.
A tile saw is cumbersome to set up and deliver water to for a single tile. A hand saw would take days and would be very frustrating for such a long cut--I'm not even sure it would do porcelain. A rotary tool (Dremel) won't have the power to cut porcelain (unless you have the patience of a tick and about 20 abrasive wheels). A score/snap cutter isn't appropriate for compound cuts at all.