Somtimes I do have to cut and splice something just because its faster and easier than re-doing an entire piece that may already have multiple bends in it. My thoughts are that splicing is fine if you do it properly. always sleeve the inside of the tube with another piece of tube. Before you put the two halves back together with the sleeve inside, make sure you drill a few holes through each half of the tube so you can plug weld the tube to your inner sleeve. If you do not sleeve it and you just butt-weld it back together, chances are pretty high that it will just snap at the weld when you roll over or run into something with the bumper.
If its prepared right, it wont snap, with no inner tube. Just bevel to a knife edge and weld it.