My take on that is "Carvin makes a great bass especially for the price"
As far as comparing it to a similar brand... Peavey Cirrus perhaps?
I think this is pretty damn good for comparison sake though I will note a few differences.
Both the Carvin LB70 and the Peavey Cirrus are extremely good values for the money.
Both have incredibly good prices on a used instrument.
Both are boutiquish, with neck through, nice hardware options, nice top woods and colors, some wood options, natural grain.
Both have there weakest point being the electronics. I have heard this alot about Carvin and some people replace there Cirrus preamp with a Millennium preamp. The electronics in both are adequate but still the weakest part.
Both have impeccable workmanship and as long as they were treated right the neck action can be extremely low and comfortable.
Both are modern sounding basses with electronics. The Carvin can bypass the active preamp though.
Now the differences:
Carvin lets you mix and match A LOT of options (woods, hardware, finish, pickups, electronics etc.) While not nearly as many options as some custom builders, a lot more than most mass producing companies. Peavey's Cirrus is mostly just 6 or so different wood combinations (Flame Maple top, Walnut top, Wenge top, Redwood top, Quilted Maple top, and Koa top) with different colors on the quilt maple tops, and occasionally I have seen a maple fretboard, but mostly pau ferro. I HAVE SEEN a couple of custom Cirruses, but most of them are stock. The customs are pretty expensive new. Oh yeah the Cirrus does have a bolt on model but no options on it. All in all the Carvin has way more combinations of options, but the option packages for the Cirrus are VERY good.
All Cirrus are 35 inch scale but Carvin can be either 34 or 35.
The Cirrus is usally slightly more new (unless of course you really trick out the Carvin.)
THe Cirrus also more on the used market but still a great value... Thick Cirrus $650 vs Carvin $500
I like my cirrus slightly better than the carvin, but I cannot emphatically say that it is ACTUALLY better. That would be up to you. I would call the Cirrus a boutique bass at a USA Fender price, and the Carvin a customizable boutique bass at a USA G&L price, though I wouldn't label the Carvin custom (I reserve that for companies like Alembic and Wishbass... just seeing if you were payinga attention lol)