HI,
eel
47 da
2+2% dodge
6% movementspeed
10% pierce resi
vs
guide
30 physique
8 da
18% slow resi
8% movementspeed
3% physical resistance!
15% cold resi
15% lightning resi
guide is clear the better one? or not? Physical resi is a strong stat, slow resi is good, and overall you get more resi, more movement speed.
But in nearly all endgame builds/guides I see eel devotion over the other one. If you need the blue affinity points. Why? Can someone explain and enlighten me 
Sailor also gives freeze res, which is on par with physical res on coolness. So Sailors all the way unless you desperately need that one free devotion point.
What’s your build? Do you need the resistances or is the dodge melee/ranged more important?
Both are good. Sailor’s has better stats but Eel is the most cost-effective constellation in the game. If you want to pump up your blue affinity quickly, Eel is your best option.
Sometimes you don’t have this spare point to take Sailor’s Guide instead of Eel s
Imagine you can’t take Tree of Life or Ishtak or Light of Empyreon because you put 4 points in Sailors’ Guide instead of 3 points in Eel.
Of course it’s best to get both but sometimes it’s not possible and you have to choose between the two.
personally I usually take both as I need them to get Solemn Watcher’s 5% DA