My history of phones: Moto v3im, HTC Dream, HTC Desire HD, Samsung Galaxy S3, iPhone 5. Currently dual-wielding the SGS3 and IP5.
Each have their pros and cons. HTC has the best auto-correct. Samsung has the best specs. IP5 has the best games.
What to get depends what you need your phone for. When to get it depends on how soon you need it. No matter what you get, a newer better phone will be out within the next 3 months.
Also, I prefer to buy the phone unlocked. I don't like the idea of paying your line carrier $30 to unlock at a later point in time.