Are some techs/wepons useless?

[javaslinger]

It seems in my limited experience so far with this game that while there are indeed a vast amount of techs and tech levels to research, many of them are virtually worthless... Or nearly indistinguishable.

Is this the case?

Also, I imagine that once you have gotten fairly strong or deep into a game, that there are really only a very limited amount of weapons that you would possibly want to make use of. Is this so? In the end, is there really only one weapon set you would want to use?

Thanks,

Ken