I have both, although I don't know if the olive on the website is the same as the large soft in earth I ordered a few months ago when it was a pilot bag.
I find the vachetta to be softer and slouchier than my LB in earth. The vachetta is also distressed from the get go, the finish is done so it does look somewhat weathered. If you can see it in person before making a decision I think that would be best. I personally like that over time the vachetta bag will show a bit of age. It is something you will have to be careful with, probably do a bit more conditioning if you get a scratch here and there. I'm debating a coating of obenauf's one of these days however I don't use this bag daily.
Can't really say which is lighter, when I carry either of these I usually have them full of stuff, haha.