I am also new to cycling and recently purchased the chromoly Zeros. I was originally looking at the Shimano SPD-SLs like you but decided on Speedplay for a couple reasons.
1) They get about 99% rave reviews from everyone who uses them which is very reassuring.
2) They offer 15 degrees of free float that is fully adjustable down to 0 degrees. This was a selling point because I am new to clipless and had no idea what I would prefer or how my knees would react to zero or limited float.
3) I felt very confident that, had I purchased a cheaper pair of pedals, I would want to "upgrade" to something higher quality before long and couldn't see wasting the $50 now.

Also, at around 200lb I have had zero issues entering and exiting out of the system like some people have claimed.