Aperture always rules. 6" is always better than a 4.5"...anything. EQ mounts have their advantages if you are into tracking and perhaps astrophotography in the future. Persoanlly, the (6") Dobsonian would be a better choice. Now, said you would do terrain obseving as well? Neither scope you mentioned is really suited for terrain viewing. A refractor is best for that. Normally if someone wants to do sky and terrain, then a 90mm f/9 or longer refractor will do just fine. Some of the rich field refractors such as the Shorty's like 80mm ST or 90mm ST from Orion or from other places can do the job...to a point. Orion now has a 120 f/5...? or the Celestron 101mm f/5 can be used to for both sky and terrain. Reflectors aren't the best for terrain, it can be done, but refractors are better suiited for that. Good Luck!!