Well, I still need to clock 1000 km (which I believe, I should do it before the end of next week) so I might revise my thoughts but as for now, here is what I think.
5th gear acceleration of YBZ is better than GS. Say if I'm riding at 80 km/h and wanted to overtake a car on a highway and I don't want to change the gear since I'm cruising and not racing and I open a full throttle, YBZ has better acceleration in this perspective. BUT in any other situation, GS150 is better as far as acceleration is concern.
Note: My opinion might change after completing 1000 km when I'll rev this bike to at least 10K RPM.
Comfort
The seat of YBZ itself, is inferior to YBR but certainly superior to GS150, YBZ's seat is pretty wide and it's a plus. If both of the rare shocks are set to middle setting (default settings) - GS150 is more comfortable on bumps & jumps but the sitting position is better on YBZ which is good - but still, if 'm going on a long tour and wanted a bike for this purpose, I will do this:
- Buy a brand new Bike (GS150 not SE) and do the following.
- Visit mechanic and fix the gear changing sound (change rubbers within wheels)
- Change the headlight
- Handlebar grips of GS150 are poor since it's a lines which hurt hands so I'll get that changed.
- Change both tires
- Do some solution for rust since it's a pretty low quality bike
- Change the plug otherwise, this bike will not give a good riding experience and can't achieve top speed (i.e. 120 km.h)
- Get better boots since GS150 generates a lot of heat when riding in summer.
- etc.
One might think, why not GS150SE - because it's simply not worth it. Before buying YBZ, I test ride my friend's brand new GS150 for 50 km and I was pretty disappointed. Whole story (including video) is on facebook on following post:
https://www.facebook.com/groups/143698125819785/permalink/634798856709707/
I chose YBZ since I really don't felt the need to change anything at all in it.
Top Speed
YBZ has better top speed and I know this for a fact. My GS150 was highly maintained. It was maintained enough that, even due to it's low build quality, GS never gave me headaches about anything whatsoever but when it comes to top speed, my GS150 managed to clocked 125 KM. After 115 it just died and it took a lot more time to time to cross 120. But on YBZ, I face no delay whatsoever to hit 120 (in comparison to GS150) and I firmly believe that it should clock 130 km/h. Time will tell. Let's see.
Stability
YBZ is more stable when riding 90+ km/r speed. The overall weight distribution of YBZ is better than Suzuki.
Initial Verdict
If you want a raw power and can deal with poor quality of bike than GS150 is a best option in the market right now. But since YBZ isn't far behind in the power department so I would suggest to go for YBZ. This bike did NOT disappoint me and it's a quality machine.
BUT
And it's a very important BUT 
If long tours is the only purpose then I would still buy a GS150 over YBZ any day since it's has great raw power but for everything else, YBZ is a good bike.
I hope, this will help you make a better decision.
You can expect even detailed review once I'll complete my 1000 km and properly check the bike.
