Here is the view from the top of the heads (black painted one is a "Vertical" 175, sandblasted one is the "Sloper"175.).... While the vertical head has an obvious increase in finned area, they both will fit on either cylinder, use identical gaskets, and will hold either camshaft.....
The main differences are internal (valve angles, and ports) but the angles that the carbs and pipes bolt on is different too...... This pic shows the BIG difference in intake angles from the side......
The intake ports are also rotationally different, so the aluminum intakes won't exchange vert to slope.... The flanges for the carbs are again rotationally different, AND a different size (between bolts).....
All of these things can be overcome with careful mods or some fabrications......
There are similar differences in exhaust port angles as well, pipes will NOT simply exchange even though they are the same diameter
The Vertical head is said to produce more power, have free flowing ports/tract and better valve angles..... I have yet to do my side by side comparison, SO I can neither agree or disagree......
You may also wish to view this site......
http://sports.groups.yahoo.com/group/CB175RaceTech/
and the "parent" site....
http://www.jrbranson.com/HondaRacer/mainpage.htm
Enjoy!.... Steve