After my Nikon d7100 rolled off the bed onto the carpeted floor (YIKES!) about a month ago, it has been slow to focus and not as sharp. So I finally broke down and took it to be repaired and rented the closest thing I could find, a Nikon D700. After I got home, I read online comparisons between the 7100 and 700 and on most specs they are very similar, with the huge exception that the D700 is full frame (as opposed to the 7100 being cropped) and the sensor size is twice as big. But the pixel count is close and most reviews say the 7100 IQ is nearly as good if not equal. So apart from the wider view that the full-frame provides (which, frankly, is not an advantage often especially since I usually like to get closer to my subjects), what's the big deal about the sensor size? I don't understand why a bigger sensor is better...and makes the camera model cost twice as much. All other things being comparable, I don't understand why bigger sensor is better? I know there are lots of technical experts on this forum...can you please explain it to me?

Ring flash will illuminate, but it will create "flat" lighting. With macro, unless you are shooting stamps or forensic crime scenes, most subjects will benefit from using directional light - from one side or another - to better reveal textures and fine details. A good way to approach this is to separate the flash from the camera with either a cable or a radio trigger. Yongnuo has a cheap but very reliable trigger, the YN-603 II. This will allow you to position the flash anywhere you want. Bounce your flash whenever you can, it will give you a more pleasing look, but in certain circumstances you'll want that "crispy, hard-edged detail" look of unmodified flash.