Its useful to also consider the northern destination / connections too rather than just abbey wood
On the flip side to to the LO option though, the dlr option would also open up connections to Stratford for geml and West anglia main line. In addition to the shopping centre itself.
A c2c connection would still be possible at West Ham. Agree less ideal than Barking but still very handy nonetheless.
Personally I think an extension of either option to Abbey Wood is sensible. There are broader aspects that should be considered besides Thamesmead itself. Without it the dlr would offer a crossrail connection at Customs House. However there would be a missed opportunity to benefit users who don't live in Thamesmead with a river crossing as you reference above.
I'm torn because I prefer Heavy Rail in general but there are compelling arguments for DLR too, especially if there will be no freight and no connection to the North Kent line. 4tph of 4 cars is a bit rubbish for a such a big build. Even if that increased in time (with a short working somewhere perhaps, Blackhorse Road or maybe up to Enfield Town even) - it isn't that much capacity or use, without freight.
DLR to Abbey Wood wouldn't offer much to anyone except Thamesmead people though - as Crossrail does the rest. And this scheme is for Barking Riverside over Thamesmead, for better or worse...
A hybrid of the old Dagenham Dock DLR proposal, following the river and swinging south to Thamesmead (tunnel or bridge) - would be odd but cover off both areas.
A new c2c station between Barking and DD might also then support the lack of a Barking/Fenchurch St connection, and decrease reliance for a whole new area on one random link.