So since you presumably have no informed opinion on this matter it seems most unwise to comment.
An informed opinion is not given at birth, so let's form one.
Both input output and balance approach work pretty well in current blockchains. It looks likely that both of them could work in combination with a tangle.
@cfb: concerning consensus of balance approach: In which case would full nodes not be able to agree on balances? Each of them stores the full tangle, so if one of them tries to validate transaction A, but sees that other nodes validated a conflicting transaction B with more PoW, then A will get rejected, similar to how it works with blockchains, no?
Just like an input cannot be spent twice, a balance cannot be spent twice either?
Proposal: Let's integrate balances, see in beta if it works well.
Worst case: If not, then cfb would have to rewrite the code to input/output, and we would start the tangle again from scratch.