Well, time to chime in. I actually own one of the bikes being compared.
I have a 2003 VTX1800S
Its the best bike I've owned so far.
Your comparing it to the m109...it will come down to what you really want, a more sporty
looking cruiser, or a more comfortable cruiser. Their both 1800CC, and the performance, while I'm assuming the m109 will be a hair quicker, the VTX will be right on its "O Ring", able to contend for sure when you factor in the rather "average" racing abilities of most actual riders you will meet on the road.
However, When looking for my bike a year ago, I looked into a lot of the sexier looking cruisers, but none were as comfortable and stable for 2-up long distance riding than the VTX.
The VTX has a more retro look, the M109 does not.
Keep in mind that the VTX has been around already for 4 years and already has a very strong aftermarket going for it...while the Suzuki is just releasing their contender. The 240 tire on the Suzuki while looking cool does make the handling a little bit harder than the VTX, but when your talking about big cruisers, handling isn't a strongpoint for anyone.
All in all, if I had to go for one right now, I'd go for the M109 if I just wanted sporty looking, but I'd go with the VTX if I wanted comfort or custimizability. Also, the VTX has a shaft drive which is much less matainence to deal with when compared to the M109.
But, if I could, I would wait for another year or two and see Honda's new news. Think of it, Honda seems to always be the mark that the other metrics try to hit. Honda introduced the VTX in 2002, and then Kawi rushed and put out a lower quality but higher cc bike (that handles like a wheelbarrow and is slower from what I've read and seen on the road), and then finally
4 years later Suzuki and Yami come to the table with their 1800 counterparts.
Honda is 4 years ahead ladies and gents. News is that they are going to be releasing their next thoroughbread next year in 2007, and while the roadliner and m109 will be hard contenders for the VTX, and maybe even outshine them in one thing or another, they are all great bikes that I would consider in the same catagory. (I wouldn't even consider the vulcan if I were you...uggghh)
But, I'll bet you that Honda's new scheme will again put their metric competitors to shame.

Thats not how my bags actually sit, it has a heavy ball of metal in the back of the bag, and its opened so it looks like it sits funny...I'll get better pics eventually