it's not a case of always do this or always do that. if you feel you can get by on your base stats from being higher level, and maybe health/resistances from your damage you build (maw/titanic hydra/cleaver etc.) then go for it. you'll be tanky enough to survive their volley of spells and you can one shot their carries. if you feel for your role in fights at that moment in time your team needs a meatshield, it can just be worth tanking up after first item even if ahead, because when you finish it you'll have damage on par with them but you'll be able to take a lot too, it just means your damage will fall off sooner.
on the other hand, solo queue is solo queue and it might just be worth going double damage items anyway since you want to carry your team mates by outputting damage if they're lacking (behind or they just suck) to keep your team in the game and sustaining them with assists or giving them the kills.
but still, put your head to it and just think about their threats, your role in fights, your team composition's function (poke/pick/teamfight/siege) and how you can best itemise to aid with the strategy you need to pull off to win.