To me, it's a replacement for the Gnome, with the capabilities being different, but roughly equivalent.
Speed is exactly the same, with the addition of XMEC.
You lose a few points of armor, but gain fire resistance.
The APGR loses a couple points of damage, but gains in range and antipersonnel damage.
The SRM rack loses range, but gains raw damage, ammo, and inferno capability.
These are the suits that complement Eyries, Gyrfalcons, and Shrikes, while the newer Omnis stick to Elementals and Rabids, and Ironholds travel via Mk.VII-Cs. >:D
EDIT: Hell, the BV is almost exactly the same, with a Stormbird Point only costing 6 more BV than a Gnome Point. That's not 6bv per suit, that's for the whole squad.