What about the difference between fibre and solid state cristal YAG lasers?

In general, we can say the solid state Nd YAG laser source is an older type of laser still used, but it has far more maintenance issues than a modern fibre laser. In contrast to the YAG laser, where the laser light is produced in an Nd crystal rod with two mirrors at each end, the light in a fibre laser is conceived into a fibre directly and guided in one way to the output fibre. Everything stays in the fibre, resulting in a very high wall plug efficiency, unlike the YAG laser, where you have critical cristal cavity cooling. Further, you need to couple the outcoming laser beam into a fibre. You can imagine the sensitivity of injecting a 100-micrometre laser spot into a 400-micrometre diameter fibre. A lot can go wrong with changing environment as those lasers are vibration sensitive. A YAG laser will produce a flatter laser beam, making this laser soft and non-aggressive on most surfaces. The fibre laser produces a more Gaussian type of laser energy distribution beam. This higher beam quality can be tuned down with suitable optics to get a flat beam type. If you consider that pulse duration is always constant with a fibre laser over different frequency settings and not with a YAG laser, your choice must be a fibre laser. Also, the dimensions of a YAG laser are far bigger because of the cooling you need and bulky electronic frequency generators. The future is clearly with the fibre lasers because of the higher efficiency and no maintenance aspects of the source itself.