I wouldn't say they are all anywhere close to the same, but there are a few top brands that seem to produce solid products. I'm a fan of Tritronics, they have excellent hardware and customer service. If you liked yours, I'd say stick with them. Dogtra has a good rep also. I've heard mixed opinions on Innotek and it probably depends on how much you abuse the gear. Their more expensive collars seem hardy, but I have a few friends who have had bad luck with the entry level stuff. DT Systems is pretty good also.
My advice is to select something from a reputable manufacturer that meets your budget and that has the range, features, and transmitter size that works best for you. Some of the latest models, like a few of the Tritronics sets, allow you to marry additional collars to the transmitter. If you ever completely lost a collar, you could replace just the collar and not the transmitter too. Or, you could add collars later if you get more dogs.