More than anything, the whole tip experience is the most individual-specific, I find. Ortofons and Spirals are good, but for my ears and head, nothing comes close to the Spinfits. For me, Spinfits insert a little farther than other tips, seal better and stay in longer/more comfortably than other tips. They are great with heavier IEMs like FX850 or Dunu DN-2000. Because of the better seal, more of the musical information coming from the driver can be appreciated : I hear more bass with better bass details, wider soundstage, etc. Other people have reported a loss of bass on some IEMs. It`s really individual. I recommend just trying them - I can supply them, and Otofon, Spirals, whatever.
Just make sure you do not push Spinfits too far on the nozzle. The last 1/3 of the tip needs to extend past the end of the nozzle, because there is flexible joint in there and the tip can rotate around the axis of the nozzle, conforming to the curves or your ear canal. If you push them all the way on and block this joint, they will be similar to other silicon tips. When installed correctly, the entire bell-shaped silicon shell which touches your ear canal should bend and rotate freely. With some tips, like Fitear, the nozzle is so short there`s no way to push them on too far. But with others, like DN2K, i have to used the spacers to keep the tips on the end of the nozzles.