Most Ork Warbiker generals prefer large warbikers units (ie, 12 man bikers / units) for survivability.
But me... I'm the Ork general who's
off at times
My prefer warbiker units that consists of:
4 x normal bikers
1 x nob with
BP +
PK
Why? It's cheap enough where you can filed 2 or 3 units of these and still fill out large standard ork mobs (trukk boyz or 8-10man nobz bikers).
Here's a 2000pt "Pedal to the Metal" list that I'm very fond of:
HQ:
Wazdakka
Warboss on Warbike,
PK, Cyborked
Troops:
4x Warbikers + 1 Nob biker w/
BP,
PK
4x Warbikers + 1 Nob biker w/
BP,
PK
4x Warbikers + 1 Nob biker w/
BP,
PK
4x Warbikers + 1 Nob biker w/
BP,
PK
8x Diversified Nobs w/ Painboy, 3x
PK, 4x
BC, 3xBP, Banner, Cyborked, etc...
Fast Attack:
1x
TL Rokkit Deffkopta + Buzzsaw
1x
TL Rokkit Deffkopta + Buzzsaw
1x
TL Rokkit Deffkopta + Buzzsaw
Elites:
5 x Kommandos + 1 Snikrot
5 x Lootas
5 x Lootas
Tactic found here:
http://www.dakkadakka.com/dakkaforum/posts/list/379582.page#3015728