Some people think a full length guide rod is a bit smoother when cycling; others can't tell and think it's psychological/marketing. The added weight theoretically dampens muzzle flip a bit, but most shooters won't notice that much difference.
On the other hand, as you have found out, a FLGR usually requires an extra tool. I have a one-piece FLGR in a couple of my 1911s and they're just a bit more hassle to field strip and reassemble -- that's why some folks prefer the two piece FLGR. Also, for those who like to "press check" from the front (I don't), the FLGR gets in the way.
Two piece guide rods have also been known to come unscrewed during shooting -- yep. Those who use them should use some of the blue Locktite glue for security.
If you want to use your 1911 as a serious defense weapon, I suggest a standard guide rod (though a one piece guide rod would be okay). If you want to use strictly as a range gun, a two piece FLGR is okay, IMO. Any online gun parts store should have a standard recoil spring guide -- Midways, Brownells.