I usually end up building above the left side colony, and wiping it out PDQ and then taking over its spot, and rebuilding there, it has 2 very nice advantages, 1 not one but 2 relativly easily defendable spots (IE front door and a fall back position, if you don't mind sacraficing your rare ore smelters for a bit.) and its also has 2 3 bar commons and a 3 bar rare with in walking distance of one another, plus tubes all layed out by the time you have 7 microwave lynx.
However it does have a seriously nasty draw back of time to actually get fully operational. You have to basically rebuild your colony at the new location, or deal with defending both colonies way early on, while eden has super early advanced tech. (A side effect of killing either colony early is they stop with the warm up of lynxes way early.)
As such you have a small window in which your building one site and slowly turning off the other site, research grinds to a slow crawl, and mean while your turning out lynx micro's and stickies like they were going out of style with using as much ore as is possible with out selling your self short on your rebuild.
To minimize this impact I basically build another land rush setup, complete with all the buildings I have to that point and enough convecs to get it done. God its hell on the ore and gets to be hairy right around the time the new colony is functional.... but its deffinatly a rush watching as those tiger acids and thors come rolling out from the other colony to fight your sparce micros and stickies. You hope and prey that you can get that vec factory to run at full tilt enoungh to keep them at bay while you finish off that rare ore research you have had going since you started your move, prey to god that they will somehow go for the old colony, now virtually,completely in shut down mode just a CC and the Advanced lab running, waiting for your to build your gorf, so you can salvage its ore value to put into more vecs.............. sometimes you make it, and then sometimes a disaster hits like that god forsaken meteor from no where and it takes out your all new CC 20 seconds after its been setup and your screwed.