The 35mm f/2.8 Macro Limited is an APS-C only lens. If you are considering use on a 35mm film camera or a full frame digital camera the image circle will not be large enough to cover the entire frame.

The 35mm f/2.0 FA is an older design but is compatible with full frame/35mm film cameras.

Both lenses get great reviews with regards to image quality, but the macro is probably just a bit sharper over the entire frame when used on an APS-C body than the f/2.0 is when used on a full frame/35mm body. Since most lenses are sharper in the center of the frame, though, the f/2.0 may well perform just as well as the f/2.8 Macro when used with an APS-C body.

In this survey of four of Pentax's 35mm offerings, the f/2.0 appears to be sharper at the center than the f/2.8 Macro. The Macro appeared to do a little better at the edges. The most significant difference I can see is that the f/2.0 shows a bit more chromatic aberration. But CA is very easy to correct in post.

The 35mm f/2.0 also seems to focus faster than the 35mm f/2.8 Macro. This is pretty much expected since a non-macro lens has a shorter focus travel from one end of the range to the other.

If I did not desire macro capability and were planning to use it for street photography, for me the faster aperture and faster AF performance of the FA 35mm f/2.0 would trump the virtually indistinguishable edge in image quality of the DA 35mm f/2.8 Macro Limited.

Something to keep in mind when comparing lens test results:

Using the linked survey, it appears the FA lens didn't fair all that well in comparison to the DA macro, especially at the edges. Looks like the DA macro is the way to go. Cheers.

It looked to me like the FA was slightly sharper at the center, where sharpness is usually more important, and the DA was sharper on the edges that are often out of focus anyway. (The only lens in that comparison that doesn't look close enough to the others to even matter is the older A 35 f/2. Be sure you're not mistaking results from that lens for the 35mm f/2.0 SMCP-FA!)

So it depends on what you want to do with the lens. And for street photography don't discount the difference in speed of focus and aperture. It doesn't matter how sharp a lens may be if the moment is gone by the time it achieves focus or the shutter speed required is too slow.

Both lenses are very good optically. Remember that a test chart is designed to utterly exploit every minor flaw that a lens may have. The differences between the FA 2.0 and DA 2.8 macro are extremely subtle. Probably less variation than you might find within a copy-to-copy test within each model. In that linked survey even the cheaper DA35 f/2.4 that performs slightly below either of the lenses you are considering produces stunning real world examples.