Though I usually lurk here I can add some input to this discussion since I own both a Series I XKE convertible and Series III V12 coupe along with the 280sl. The positives of the SL over the e types: ease of getting in and out, classic styling, no blind spots with the hardtop on. I find the SL great to use around town running errands. On the highway the car is busy though acceleration is good up to about 80mph. The Series I to my eye is one of the greatest automotive designs of all time. It garners more looks than the other 2 cars combined. Around town it can be a handful at low speeds. At 6' 1" and over 200 lbs. getting in and out with top up is challenging. I hate to park it anywhere because you fear someone backing up in an SUV is never going to see it. On the highway is were the car shines; fast, great cornering and a surprisingly comfortable ride. Even though it is considered the ugly step sister of the E series the Series III is the car I take when I want to just go for a ride. It has a longer wheel base than the Series I and is easier to get in and out of. The power steering makes around town trips easy and on the highway from any speed the car accelerates with joy. Though I have not had the guts to take it much over 100mph it still has plenty of room from that number.
I feel fortunate to be able to own all of these icons and have great respect for the owners of each and the companies that built them. On a side note my Jags have proven to be extremely reliable and have had fewer repair bills than the SL. In fairness the SL had a hard life before I bought it 20 years ago and I had to learn its mechanics on the fly.
Enjoy your cars and drive 'em like you stole 'em
Joe
