Take it from another "nube". I spent 30+ years  grilling on Webers (Smokey Joe, Kettle and Genesis) and was ready to take the next step up to REAL BBQ.  I did LOTS of research beginning in January and it was quite obvious the WSM was the ONLY way to go when it came to back-yard "low and slow" smoking.  I pulled the trigger about a month ago and have absolutely no regrets.   The Genesis still gets used about 2-3 times a week, but Saturdays and/or Sundays are for smoking.   BTW, my wife first looked at me with one eyebrow raised when I showed her the WSM 18 1/2". She figured it was just another "guy toy"  that would get stashed into the corner of the garage.  After the bacon and ribs I smoked my second weekend, she's a convert too and is always looking for things to smoke.  
I have nothing personal against anything "Brinkman", but  it's like the difference between buying a Toyota or a Kia. Both  are decent enough, but one is built better and will last longer.  So... keep the Genesis and buy the WSM. I prefer the 18 1/2" model simply because it's the right size for just two of us (except when the kids are home for college).