I'd want to be one of the arrancar living in Aizen's palace. They got to chill out and bullshit their days away. They weren't strong enough to get sent to the front lines so they lived a pretty carefree existence as long as they didn't get too big for their britches and go out of their way to get into trouble. Regular people in Soul Society would be a distant second choice, but their lives really suck. It seems like you're either in the Gotei 13 or you're living in crippling poverty. Being a shinigami sucks as well since you're always having to go out there and fight ridiculously strong people.
If I had to fight and for some reason I actually wanted to fight, I'd prefer to be a dual-wielding Vizard. My Zanpakuto would be called "Formless" and "Nisemono". Both of them look like a single glove. Nisemono's shikai is called out using the phrase "Replicate, Nisemono" and it lets me replicate the powers of any shikai its come in contact with use them either straight from the glove or channel them into another Zanpakuto grade weapon. The more I've touched the replicated sword, the more complete and power the fake version will be. The Bankai version does the same but for Bankai it removes the more contact rule and replaces it with me having to actually train with sword in that form. Formless is released using the phrase, "Destruct," which removes all of it's powers and turns it into a sword that reduces the combat strength of any reiatsu put through it by 50% but maintains 100% of the durability of a zanpakuto, which is perfect for me since it can then becomes receptive to Nisemono's abilities or allows me to wield a standard storm when Nisemono's gloved form isn't effective. It's true shikai power is called out using "Construct," which is a one time use ability that permanently forces it to remain in whatever state it is currently in or that Nisemono has put it in and changes the maximum power output to 75%. The Bankai version is the same, but does that for Bankai and removes all power reducing impediments for both forms.
I like the combo because there are pros and cons to it but it gives me incredible versatility in combat.