I've ran a welded 14FF in the rear of my K5 for well over 10 years now, basically whenever I swapped in the 14FF back in the day. My thoughts were to try it out because it was free and then upgrade to a Detroit if needed. Well......still have the welded diff. With the 14FF you can easily weld just the spider gears to make a mini-spool which lets you easily swap in a Detroit if you decide down the road. I have ran it with 35's, 38's, and 39.5's over that time. While this thing was never my daily driver with the welded diff it did get driven to and from the trails and I drove it fairly regularly to work and such for many years. The rear tires did wear quicker than the fronts but it wasn't extreme. As mentioned above it is noticeable during low speed sharp turning maneuvers in parkings lots and such but never really a problem. I don't notice anything at higher speeds including up to 70 mph back in the day (the current unbalanced trail rashed 39.5's don't allow that fast).
If it was my daily driver I probably wouldn't want the welded diff, or a spool. But for a weekend trail toy I think it is a good and cheap option. I was one of the first in our club to run a welded or spooled rear diff and now it is pretty common on trail rigs because it works and is cheap. There are several guys who also run welded or spooled front diffs on their trail rigs now, but do prefer something like a Detroit or Lock-right.