Hi Santi. Welcome. Nakano is correct. "Strongest" and "best" cannot really be answerred without further refinement.
Depending on what you mean by strongest? If you mean "reliability", "strongest lock", "thickest tip" etc.
Where Spyderco is concerned, use would matter most (since function is primary). Even if that "use" is collection, some are more collectable than others.
If you are going to carry it, then size vs local law is a question, etc. Srongest for it's size?
This is a great place to learn about Spyderco products. The forumites that visit here have excellent knowledge, long memories, and ask hard questions.
sal