Well..the BK 9 was my first big Becker and is my all time favorite knife. If I could have only one...BK9. I never go on a hike or camping trip without it on my hip. But I am very infatuated lately with the BK15. I use it everyday. There are also a lot of people getting the BK15 here lately due to the discounted price. So all the discussion, mods and pics of it going on right now is a lot of fun. I payed $80 for mine when it was first released and I dont regret it a bit.
I have all the current Becker's in production except two of them. I dont have a 5 or 10 yet. I have noticed the four I always use are the 9,14,15,16. I edc the 14, never leave home without it. Any chopping, bush clearing, tree trimming, firewood = BK9. The 15 does a lot of kitchen work but can do daily tasks and bushcraft any time I need. The 16 is just awesome for all out door work and a great companion to the BK9.
Ok, hopefully that answered your question.