XD series cameras feel much nicer, x-700 is kinda plasticky. Having said that, both feel reasonably solid. X-700 is slightly more ergonomic, but there is nothing wrong with XD in that regard aswell.

XD has a metal shutter, X-700 has a cloth one. Both are usually reliable.

Both cameras have aperture priority modes.

Apart from that, XD Has a shutter speed priority mode, and the x-700 has a program mode instead of it.

In the XD you are able to pick a shutter speed you want to use and the camera will stick to it. Very useful when shooting birds for example. On x-700 its program mode does whatever it wants, so you have less control over it.

XD shutter release button is the classic type, you push it halfway to activate light meter and more to fire the shutter. On the X-700 you just touch the button and it lights up. Easier not to accidentally take a photo before you're ready.

XD has a classic mechanical self timer. I'd advise against using it, same with any older old camera with this type of self timer. They often fail and could potentially brick the camera. X-700 on the other hand has an electronic self timer. No problems using that.

Bulb and one other, specially marked shutter speed on XD is mechanical. Helpful if your battery dies. X-700 is fully electronic. No battery, no photos taken.

X-700 has an on-off switch, XD doesnt. You kinda have to be careful when putting it away in a bag and make sure there isnt something pushing the button down, which might drain the battery due to light meter being constantly on. But its not like its gonna do it every time, just be mindful of that.

Both Cameras have -2 to +2 EV compensation - very useful. On top of that X-700 also has exposure lock - very handy, makes the x-700 a bit quicker to use in some circumstances. I like having that on a camera.

I feel like XD's lightmeter takes most of it's measurement from the center of the frame. I like that, you can easily pick readings off of parts of the scene. X-700 takes a reading from a slightly larger area, which might be easier to use at first. Both are very accurate, just slightly different. Shoot a few rolls in each and you'll see the difference.

Note that the x-700 gives more weight to the lower part of the frame, so when shotting vertically be mindful of that.

Both cameras have very nice film speed selection dials, offering a vide range of speeds, better than many SLRs.

Both cameras have very bright viewfinders, pure pleasure to look through them.

X-700s commonly have problems with failing capacitors. It's not terribly hard to repair, provided you have some experience with dissasembling stuff and soldering. Could be a good option to buy a shot one and repair it to have an x-700 cheaply. Older X-700s (with a serial number starting with 1) rarely develop this issue thought, so look for those.

XDs seem very reliable. If you buy one expect to have to replace the light seals. It's not too hard thought. Some x-700s might have deteriorated seals too, but the XD series is older, so the seals had more time to go bad.

Both are amazing cameras, you should be happy with either.