I'm looking into buying a 98 sls, but might want a sts. I know the engine differences but what about the interior options, like heated seats and bose system and all the good stuff. What is standard and what is optional with both models? And is it true that the sts model will go 150 but the sls model is limited to some where around 120mph?

 

Speed limit is set at the factory according to the speed rating of the original tires. The little difference in HP won't even show at "normal" driving, or the SLS might even show a little more git-up-n'-go because of its higher torque.
The STS came with an analog cluster while the SLS could have it as a Sport Package. The SLS had side mouldings and wider tail lights (neater!). Normally the STS had more standard features but none that the SLS could not be ordered with.

 

If you want performance and goodies then you will pick up STS .SLS is limited to 112 mph .From '98 and up they have same tail ligths .You can also get an SLS with STS package but still you wouldn't hit over 112 mph .
SLS has a softer suspension to STS

 

Generally speaking conventional wisdom suggests that the higher torque lower HP motor is a better choice for overall driveability. This is the reason this motor goes in limos, it has more grunt where you need it. I have had Cadillac salesmen tell me that even a Deville or DTS with that motor can take an STS at the stop light Grand Prix. Personally I like to drive fast but I have little occassion to drive over 112 MPH since it is both dangerous and foolish.

 

My STS compared to my folks eldorado is about a wash (IMHO) My STS weighs more (I think). From a stoplight.. well both light the tires.. so its hard to judge. The Eldo wont light the tires after 25-30 my STS will (its winter here, summer I have no idea when pavement is warmer). But I do agree, the eldo seems to have more low end grunt when the tires hook up. My STS seems to be sorta, hmm, doggie at low rpms when kicking it down compared to the Eldo. but after about 45-50 the eldo doesnt seem to push me in the seat as much.

One thing i find wierd on the STS, somedays a lead foot will light um up all the time at 30, another day its almost like the tranny wont want to shift down and it just builds speed.

I like 2 doors, so the Eldo would be my pick, as far as SLS-STS.. they look the same to me I think the extra HP and stiffer ride is really the "major" differences. If you owned either i think you would like it.

Love mine.