The only reason to slide to avoid a tag at first is if you are returning from the attempt to get to second. From batting, it’s an automatic (“force”) out.
I assume that you can get to first slightly faster by diving. Your center of mass is travelling at Xmph while running. You can extend your leading foot maybe 3 feet in front of that, depending on timing. If you dive, your upper body and hands can extend maybe 5 feet ahead of your center of mass due to outstretched hands, assuming you maintain Xmph while diving (good question) and cannot dive faster than you run. Once you make contact with the ground and start to slide, your speed will decrease drastically. So dive.
Top fit athlete running speed is let’s say about 20mph or about 30fps. (60mph =88fps) a dive which gets you there 2 feet sooner shaves about 1/15sec off your travel time. That’s almost photofinish territory.
of course, too, a fit athlete’s center of mass is probably higher on the body than a typical person’s, meaning arm reach advantage when the body rotates horizontal is less.