TIG does have a learning curve but I still think it's a good choice for a hobbyist (especially if you make bike frames). The problem with arc welding is it's only really suitable for thicker material. If you need material that thick then you're probably making something safety-critical, which usually isn't a good idea for a beginner, or you're making garden furniture and will end up spending more on unnecessary metal than you save on the welder.

MIG is easy, and can do thinner materials, but not bike frame thin. However this is a good choice if you also have car bodywork projects coming up. TIG can be used for that too but it's harder.

TiG is the only process that can really do everything, and works with all thicknesses from 0.5mm upwards.