Hey bud,
The major differences between the 2 that I have discovered are these:
1.) HAWT (horizontal axis wind turbine) is better than VAWT (vertical " " ")
a.) in conversion of wind speed to mechanical force by about a factor of 1/3 at least because of better angular encounter to the wind (meaning it has all its conversion mechanics are directed in confrontation with the wind and counter force from the turbine (blades, etc.) itself is negligible).
b.) It has a lower initial speed for the start of generation due to better torque conversion.
c.) It has a broader base of understanding and use in history.(Easier to get fixed and find parts for.)
You can buy blades for a HAWT.
You'll have to make your own VAWT vanes.
2.) VAWT is better than HAWT
a.)in that minor directional fluctuations in wind direction do not mean re-orienting the blade assembly to face directly into the wind. It may not seem like much, but a 10 degree shift in wind direction can cost you a lot of production time until a HAWT is able to reposition itself into the face of the wind again.
b.) It has lower initial speed needed to start turning (NOT to be confused with initial speed for generation start!) and it does not need a helper motor to start spinning as some HAWTs have to have (the bigger the blade, the more necessary a starting motor assembly is).
c.) It's quieter. The larger area of the vanes and their shape do not have the tendency for (THWUCK, THWUCK, THWUCK) noise pollution.
d.) Its lower turbine turn speed and more continual (but lower) power output are supposed to mean that it can be mounted at a much lower height than a HAWT. Some companies even advertise rooftop mounting (no extra tower).
Those are the hard and fast "rules" I've found in my quest to build a VAWT after I saw a blurb about Mag-Wind (or whatever the company is calling themselves this year) that has a VAWT design that makes a lot of sense to me, but has some pretty unbelievable claims for efficiency.
I think it might be a design that could be tweaked a little, and it is the most plentiful free energy I know of at the moment.

Good production to your build!