I hardly have problems with crimp connectors. Use the right crimping tool. Some crimping tool are made for non insulated buttsplice and will cut into the insulator of the splice. For a better look, you can stagger the point of splice so that you won't get a big bulge in one spot.

Sometime the insulator of the wire can get stretch out far enough that it is out of the sleeve of the crimp and the wire will be expose. Usually I seen this happen when the electrician strip back the insulator to far back and not trim the copper wire resulting in the wire insulator not insert fully into the sleeve or if the insulator of the wire was pulled. You can alway use a shrink tube to slip over the splice and that will help prevent corrosion and a better look. Before heating the shrink tube, you can squirt some clear silicone into the shrink tube then apply heat to shrink it. The excess silicone will get push out during shrinking. This will make it waterproof.

Soldering is more a secure way of joining small wire assuming you get the wire hot enough for a good wet flow of solder and not a cold joint. Becareful when you remove the soldering iron. Sometime the solder will follow the direction of the iron and create a sharp point at the splice. That point can cut through a shrink tube and create a short.