The key here is that the OP plays against 10 races. That will invariably mean multiple types of weapons and defenses to counter. As a result, it makes sense why using a dual weapon type approach could work well for the OP. I'm not sure what difficulty he plays, but that also makes a huge difference. I usually can't afford the time and effort to research two separate weapon lines.I usually play small and medium abundant maps with fewer AI. I also start warring extremely early. Sometimes I strike before I even have a chance to research any weapon lines at all.A big factor for me is stealing technology through invasion. Since I play at suicidal, I will invariably steal far superior offensive/defense technology. I will usually research logistics and hull technology to take advantage of the stolen tech.
What I tend to do is make a jack-of-all-trades ship. However ships of different classes will specialize in a particular type of weapon and defense depending on the war theater they are assigned to. This flexibility allows me to redeploy them to other areas where conflict has risen up. They can usually hold the line until a ship specialized to that race can get to that sector. My ships posted here:
WWW Link have for example 6 available Medium hulls to play with and specialize whatever the need be.
In the regular sandbox games I will always play above Normal. The exact level depends on my mood.