I find Navy Cruisers the best for lowsec ratting and anoms.
Navy Cara sporting AMLs and a PvP fit can tank and easily eat through rats and anyone that decides to spoil your fun, that or use a HAC. Like you said, AFs are probably the best for ninja ratting, the only problem being you're there longer.
My 0.03ISK: Use a shiney Cruiser if you can afford it or stick to AFs for ninja ratting.
Plain Ol' AML Caracal will melt the face off anything small that tries to tackle you as well. It's also less of a Gank Magnet.
EDIT: It also makes great bait, because you can shred their tackle, align out and if your support can't take what arrives next, you stay alive:
[Caracal, AML/LSEs/Destroyer]
Ballistic Control System II
Damage Control II
Large Shield Extender II
Large Shield Extender II
Y-T8 Overcharged Hydrocarbon I Microwarpdrive
Invulnerability Field II
J5 Prototype Warp Disruptor I
Assault Missile Launcher II, Caldari Navy Bloodclaw Light Missile
Assault Missile Launcher II, Caldari Navy Bloodclaw Light Missile
Assault Missile Launcher II, Caldari Navy Bloodclaw Light Missile
Assault Missile Launcher II, Caldari Navy Bloodclaw Light Missile
Assault Missile Launcher II, Caldari Navy Bloodclaw Light Missile
Medium Anti-EM Screen Reinforcer I
Medium Core Defence Field Extender I
Medium Core Defence Field Extender I
Hobgoblin II x2