I have the DPMS 308 AP-4 Carbine and it is not any heavier to carry than my 243WSSM 20" AR15 nor is it any more cumbersome to carry than my 223 H-Bar in 223. I really don't know where some of these guys get their info but I have plenty of experience with both platforms. I also have the LR308 24" target model and that one is the heavy beast.
The DPMS 308 carbine is awesome with 110 V-Max or 125 Nosler Ballistic Tips for predator hunting. It kills dogs easily out to over 400 yards just like the 243WSSM does.
Dtech can build you a 30WSSM that will indeed provide you with some grin factor but you will have to be into reloading to enjoy it, no factory ammo is available.
The down side to the 308 platform is the costs involved, it can be nearly 3 times as spendy to build a 308 based AR. I know this for sure since I have 3 of them in my safe in various stages of build.
The best thing to do is just simply find yourself a DPMS 308 online and order it then have it sent to your favorite gun dealer for transfer. Or pickup one of the new Remington R25 models in your favorite caliber, Cabela's carries them in 308, 243 and I believe 7-08. The R-25 is made by DPMS so the mags will work in either.
Bushmaster sold their 308 rights to Rock River Arms, it is available but I have never seen one yet. I have fired the 308 Bushmaster and it had all kinds of feed problems maybe that is why they sold the rights to another company willing to take the time to sort out the issues.
Armalite is another great choice for the AR10 308 rifles and carbines. They are very accurate and reliable with the new Gen II mags.