Alright, lets look at this objectively.
80 Health, 6HP every 5 seconds, additional 5 damage on attacks against minions, 20HP over 10 seconds after being hit.
8 Attack damage, 80 HP, 3% LS.
the HP cancels out. 8 AD verses the shield passive, is a 3 damage difference on AAs against minions. But otherwise, Blade has an 8 AD difference in all other regards.
Now for sustain, 3% LS is 3 HP gained for every AA, for ever 100 AD. Naturally, most champs won't start with 100 AD, and their base AS will probably start around 0.60-0.66 ish. So I would guess, maybe 2 hp per second if they keep attacking. Shield would likely have more than that if the passive keeps getting proced. It's providing 1.2 HP per second as a base. and if it's passive is proced, it adds another 2 HP per second.
Looking at the stats, I would argue that doran's shield is the superior item when if comes to sustain and trading. Especially early on, but Doran's blade's LS component should otherwise be more pronounce later on when additional AD and AS is built, but shield is better stand alone. (Which might make it the better Doran's item in general, depending on what you expect from that starting itemization)