When I went to my info seminar the doctor there was clearly biased towards the bypass. I chose the VSG to avoid the food restrictions and malabsorption. It also just seemed more physiological - it's not rerouting the plumbing but rather resizes and reshapes the stomach. One reason I have heard that people opt for the bypass is reportedly people lose more weight - percentage wise - than the sleeve. I have trouble with this statistic - it's far to generalized and of course also include people who regain their weight back. I haven't seen any really useful data broken down by age, gender, weightloss level etc. Also, much about what you hear about the sleeve data incorporates results from early surgeries. When the sleeve was used as a first step before getting the bypass the sleeves were bigger. Today's sleeve bouge sizes are typically 32-40 fr. Most early sleeve bougies were over 60 fr in size since they were expected to precede a gastric bypass.
Another reason why people opt for the bypass is it theoretically reversible. You can theoretically reconnect the stomach. This reversal is extremely rare - it is a far more invasive surgery and far riskier (and far more expensive) than the original bypass.
Ultimately, as everyone else said - you need to determine the best option for you. Most importantly - fine a surgeon you trust and are confident with.
G