There's no difference other than the physical design. The idea was to decrease packaging as 6 come in one case instead of 1 case per LNBF.
I'll give you some input though.
Across the board, the Slimlines have slightly lower signal strength. EA, for example, on the original style, I would see signals for the 72/61.5 of about 51/64. On the Slimline 46/62.
Same with the Westerns, with a larger discrepancy. On the old style, 75/77/57 were average. With the Slimline - 72/67/52.
Also, the LNB Brackets are terrible. They have a criss-cross of strengthening ridges and with the sharp upturn, it's difficult to push a cable end through them. Also, as per usual, Dish Engineers in their typical dumb way of doing things kept the method of putting the brack mounting screws in from the bottom, but the brackets have a captive nut now that EASILY gets cross-threaded. Now, on upgrades, imagine, it's freezing out, you're at the top of your ladder, reaching up to put this new bracket on an old dish, the cable is stiff from age, making it harder to hold it together, while you push and hold a screw up from the bottom, get your screwdriver on it and get it in without cross-threading it....smh.
BTW, if anyone of you self-help guys ever needs to mount one, putting the screws it, do not tighten them all the way until you have the LNBF mounted, or the bracket where the LNB attaches will not line up correctly.