I'd recommend a XB9 or XB12 as a first bike. They're about the same from what I hear. One just favors revs over torque. I started on a SV650, as have many others. It's the gladius essentially, the previous version. Same engine.
The XB12 isn't much quicker, to be honest. It's got a little more of a grunt pull than the SV650 in the midrange, maybe 15-20% more, but they're both slightly too much for a beginner in the upper rpms (as in pulls out from under you, almost). You can get yourself in trouble on either if you dick around, they both felt equally "dangerous" to me as I learned (1 year on the SV, then the XB). However, the powerband is so linear, that it's predictable and you won't find yourself in trouble unless you deliberately do it. So, the power is perfect for a beginner. You won't outgrow it quickly, and it's predictable. I4's have a less linear powerband, and the sudden power peaks can be spell disaster for a beginner.
Being that the power is manageable on both for a beginner, I vote Buell for handling. The hardest thing to get used to on a bike is maneuvering the 400+lbs. The Buell just has a lower center of gravity, and literally feels like throwing around a bicycle at times. It feels like a 200lb-300lb bike. The SV has a higher center of gravity, and feels heavier. You're more likely to drop it on a mistake. You need a lot of muscle to save it from tipping on a mistake, the Buell you'll barely notice the weight shift. I'm talking slow rolling in a parking lot, where most drops happen. The only downfall I can list, is that I feel like I'm spoiled with the Buell, and wouldn't be able to handle another bike afterwards because I've been spoiled with the bicycle low gravity feel.
Only edges I'd give to the SV, are cheap mods/parts availability because the engines are everywhere, reliability, and smoothness. The Buell shakes the ground and almost feels rough at times, takes getting used to.
Oh, the Buell is also easier not to stall due to the powerful torque, and to launch from hills, etc. That could help a beginner.
So, the Buell is the better bike for power, handling, etc, without being too much. The SV just has the edge in parts/reliability.
Oh, another side note. I vote Buell again if you plan on any highway cruises. That's where both bikes fail, in my opinion. They don't pull hard on the highway, and sit at high rpms. But, the 650 just loses too much, the Buell is comfortable pulling about 20mph more. In other words, the SV/Gladius feels like you're pushing it around 60-70mph and doesn't pull great. The Buell is comfortable cruising until 75ish. Something to keep in mind if you're on the highway. They both obviously accelerate past those points, but the SV is sitting at like 6k rpms screaming down the highway. The XB isn't much better because it has 1 less gear, so it's at like 4k rpms. Both suck for highway cruising, but at least the XB is a little quieter and more comfortable.
