Buying new is always good, but when I bought my new trailer end last year, I just decided to go as cheap as possible. Fibre glass is very nice, light weight and all, but soooo expensive. I need a trailer for long weekends, and annual holiday, I dont use it that much. Thats why I decided to go the cheap route.
I'd say a good balance between very good, and cheap stuff, is a Venter. But they'll cost you in the region of 10 grand. I bought a Campmaster Road buddy from Makro, very happy with it, but I must say overall finishing doesn't come near a Venter. So decide on how much you want to spend, how much you gonna use it, then decide on that.