Opinions differ, but mine is that after using plastic tanks (Paterson) for many years I got a stainless steel one, and it was wonderful! I've only used a steel tank for the past 40-odd years. If you get the tank size for 120 film, and a 120 spiral and a 35mm spiral, you can do both. Once you get the (easy) knack of loading the film starting from the centre, it is just a lot easier and foolproof. Steel tanks and spirals are also easier to rinse and dry and never break. Unfortunately I don't think they make them any more, so you have to find them second hand. Kindermann is a good brand, but there are also some good American and Japanese ones.