Its called ELS-H (H stands for Halogen).Only ELS v6 supports the halogen feature where you get a rotating effect.However,v6 has been proved unstable for many people (many,not all) so be careful while using it.
How come I don't see a lot of lightbars that look like they have rotating lights anymore in the game (I don't see people using them, I guess is what I'm trying to say). Like this http://www.youtube.com/watch?v=iuzZYNoV3no
They all use the LED kind of lightbars like this
I'm just curious. I like the older lightbars the best :P
The flashy one uses ELS. ELS is nice because it actually looks more like real police lightbars (very, very few cop cars still use rotating lights; ****, NYPD uses a flashing Vision SL [the only rotators are the white lights flanking the center pod, and they also serve the role of takedown lights/spotlights]). There aren't a ton of non-ELS cars used. I see where you're coming from with the "like older lightbars"; I'm also kinda a fan of rotators. However, modders don't like IV lights as much.
EDIT: Dhruv, he was contrasting non-ELS with regular ELS (a non-ELS MX7000 vs an Arjent). OP: ELS-H lets you use some ELS features (e.g. lights on without the siren, traffic advisor/secondary lights, etc.), and works the same way as ELS, but gives the appearence of a rotator.