We use the whale of a tub and our baby LOVES it! We started off with the sink and that worked okay. We found that she was too squirmy in it, and as she didn't have head control yet, it was fine for a quick bath. We almost dropped her a couple of times and when she squirmed we did bonk her head on the side of the sink once.
We then took her into the big tub with us and she just loved the water. She loved to splash and kick in there and it was really helpful with her gas (breaking it up) in the evenings. Only we didn't really want to have to fill up our big tub and bathe with her every night (a matter of convenience and time and cost - our tub is really deep and takes a while to fill for an enjoyable adult soak).
That's when we decided a tub was essential for us. I did a lot of research and this one was recommended a lot. I like that it's designed for newborns and will transition over to baby stage. She can lie back and soak in the water - she just loves to splash about and kick - and she's totally supported. She's just over 3 months right now and she can still sit with her bum on the green bar (she can't sit up yet so this is awesome). Baby loves her bathtime and this tub has been great. I didn't think one was essential before she was born but it's one of the most valuable pieces of baby gear for us.