Hi Tom- that's a great question you have and can offer my observations. I have experience with both DOT spec lighting and true E-code lighting on my '94 E500 (38.5k) and also have Bosch OEM DOT lighting on my '94 E320 Coupe (95k).

E500 DOT spec OEM lighting is manufactured by Bosch and the E-code lighting manufacturer (I used) is manufactured Hella. I believe that e-code W124 lighting units are also available from Ziegler, TYC, & Fifft (sp?) among others with various build/ materials qualities.

In summ:

>Here is a ranking of reg. drive lighting effectiveness based upon my layperson observations w/ stock 55w/60 bulbs:
1) Hella E500 E-codes (defined as "baseline + 100%" = supreme)
2) Bosch DOT OEM E500 (defined as "baseline + 40%" = best DOT spec W124 lighting)
3) Bosch DOT OEM E320 Coupe (defined as "baseline" = above average vastly improved lighting vs. pre '94 W124's)


> The "headlamp assemblies": Bosch DOT vs. Hella E-code E500 are NOT identical: a) DOT E500 vs. E-code E500 units. Even moreso in comparison of DOT regular '94 W124 units (Euro look versions) vs. DOT regular E500 units. Naturally with these differences come differences in the effectiveness of the lighting.

There are easily observable differences in materials and interior construction between the DOT Bosch units vs. the Hella E-code units- resulting in more effective lighting w/ the E-codes. You may wish to search for more of my observations posted in Michael's E-code lighting thread (thanks again Michael for passing the PUMA supplier on to us- the Hella product is definitely the real deal- but not cheap by any means).

>Both Hella and Bosch units appear to be of the highest build quality- but with different build/ project specs.

I haven't converted my '94 E320 Coupe to E-codes so, I'm not able to offer a comparison on the relative ease of conversion between W124's, however, I can mention that the conversion on the E500 was very very very easy and fun. On our 1994 E500's there is no need to update/swap/change the stock wipers and/or motors since they work perfect with Euro-spec lighting units.

On a scale of 1-10 (10 being most difficult), the procedure is ~a 1.5-2.0. I would suggest masking all painted and shiny areas that may risk scuffing/ scratching (thanks Dcraig for the passing on the hint) and finding a lazy weekend afternoon to enjoy the install process.

I'd also like to pass on a tidbit I gathered up from browzing around re: headlight effectiveness- as a vehicle ages, the lighting effectiveness is often reduced quite significantly due to lense wear, impurities inside the unit itself, etc. ...so folks that have ineffective lighting, E-codes not excluded, may not be receiving 100% all of the benefits of their light's design and intent.

I had only 38k on my E500's odometer w/ stock OEM Bosch units and noticed a marked improvement in lighting effectiveness w/ the Hella e-code conversion. Other's results may yield varied and wide opinions of this upgrade based upon the quality of the e-code units used, wiring conditions, etc. (and personal preference).

Note - though- - that there are construction differences between W124 E-code units: regular W124 vs. 500e/e500 so, performance gains may not be similar.

I'd agree 100% with Jim's comments also.

Hope this helps.

-fad

PS- if one resides/ drives in well lit areas....one may not require or need better lighting than what comes OEM DOT stock on the '94 E500's