You know, the nice thing about this forum is that I am sure there are several people that have both of them, and they aren't going to bash either cooker. The egg forum tends to have people (not all, but some) that are crazy excited about their eggs, and they don't believe that anything else compares. I bought a WSM first, and I had it as my only smoker for 9 months. I thoroughly enjoyed it, and got addicted to BBQ like everyone else around here. I bought my Large BGE from the local classifieds a year ago (never used, but no warranty as I wasn't the original owner), and that got me hooked on eggs. Its a fuel miser, cranks up to incredible heat for searing and pizza, and does some serious low and slow too. How does the food compare? Honestly it's the cook, not the cooker (to borrow the famous cliche). But, the egg is the cooker in the winter, and when its windy. It simply does not care what is happening outside the cooker walls. I am embarrassed to admit that my WSM has been at my parents house since I did the Christmas prime rib on it for the family.
So really, they are different cookers, but many of the same results are achieved. My comments may have cast a negative light on the WSM, but that isn't the case. I love its portability, and the bang for the buck is unmatched by anything else. Eggs are heavy, and crazy expensive. I bought a small egg to overcome the portability issue, but honestly, it sits right next to the large in my backyard and never goes anywhere. Kettles and the WSM handle that duty, and they handle it well.
To give you a gauge of use, here is my usage for the last few days that I can remember:
Saturday: ribs on LBGE
Sunday: grilled pineapple on Performer
Monday: nada, went to neighbors for dinner
Tuesday: chicken breasts on SBGE
Wednesday: Corn on the cob on the performer
Thursday: steak on SBGE
Friday: BS chicken breasts, quesadillas, grilled pineapple. All on SBGE.
Tomorrow: Ribs on performer/SBGE (cant decide which yet)
Yeah, I had to kick off the grilling season big this week. The pineapple keeps the wife/family liking grilled stuff, so I throw that in there. Anyway, I am split on the use really, they all have their place and strengths. I honestly could talk/type about this for hours, so I will let someone else chime in. Good luck on your decision, you will love the egg if you get one. If you don't, your food will not suffer, it will still be great. But get it anyway, its a fun toy.