Which company makes a better 27mm swaybar, h and r or agency power? Is their a company that makes a sway bar larger than 27mm?

 

You don't need one that big. Trust me you don't want that much oversteer. My RRE 25mm makes the car plenty tail happy.

 

You need to be specific about which catagory it's better in? Please expand the question.

 

I have the 24mm Hotchkis, and it made my car pretty neutral with 100% stock suspension on the middle setting. I can rotate out the back on the street much more often than I could before - but mainly only in 1st. I'm sure if I moved it to the middle, it'd be close to on-demand in 1st gear.
On the track - where you have a lot more grip overall - I could drift through some pretty high-speed turns under full throttle. This is so f'in fun! And by drifting, I mean just a bit of side movement for a short period; nothing like a full drift or anything insane like that. Hopefully it makes sense.

I can't speak to any other rear swaybar; sorry.

Be sure to factor in your possible springs or coilover setup to match up with your swaybar choice as well. G/L.

 

Which of the 2 swaybars listed above is constructed better? And which one is stiffer of the 2 listed above? Thank you

 

I have a cusco 27mm sway bars (front and rear), and it keeps the car planted! It doesn't want to get loose whatsoever. I'd definitely suggest those two if you can, but if you're still on stock suspension, a rear swaybar will suffice.