|My blue line Beorning|
One of the first things I noticed was that it was so much easier to generate wrath in blue line compared to red line. Having Hearten provide wrath at a low level on a short cooldown was fantastic - now I could reliably generate wrath and have a heal-over-time effect while my character transformed into a bear and she would still be healing and generating wrath for a little while, letting her stay in bear form for longer.
She was a lot less squishy in blue line. My red line beorning would frequently drop below 50% health, but that has been very rare for my blue line beorning. In blue line, she could handle a lot more mobs - she took on 8 wargs in the Lone-lands near where you summon Shadepaw for a quest and survived; she killed one in man form while generating wrath, switched to bear form, killed 3, switched back to man to heal and regenerate wrath, finished off another one, switched back to bear and killed the final 3 and still had about 40% health at the end.
Regarding being less squishy, I think that is largely due to the buffs and debuffs available in the blue line. For man form there is Guarded Attack which increases armour by 10%, while in bear form Claw Swipe reduces the amount of melee, ranged and tactical damage dealt by nearby enemies. Trait points spent in increasing vitality also helps. The red line focuses more on critical strikes and bleed damage rather than survival, although they do have Expose which reduces enemy mitigations by 40%.
Blue line also has slightly more AOE potential, with Biting Edge in man form and Claw Swipe in bear form, while the red line only has Biting Edge and has trait points to make it single target (although why anyone would willingly give up their only AOE attack is difficult to fathom).
The dps was lower and fights took longer in blue line compared to red, but that is to be expected. Out of curiosity to see how big the difference was, I killed ten level 30 Bog-wardens in Harloeg, Lone-lands, in each spec; gear, virtues etc. were the same. Note, my character doesn't have her virtues and gear maxed for her level, so better players would get better results. She used the same type of rotation for both specs - shoot to pull mobs into melee range, use each of her man form attacks to generate wrath then switch to bear form and use Thrash until the mob was dead (usually 1-2 Thrashes). Using Claw Swipe or Bash wasn't necessary and increased the fight duration.
Here's some data:
The red trait tree is good at single target damage while the blue trait tree is good at surviving any situation. Having tried levelling solo with both specs, I'll be sticking with Blue - it feels more like how I imagined Beornings would play; changing forms often and being tough.