I prefer Razer, but I will never say it's better than Logitech.
Razer:
- Deathadder is fantastic, it's imo the most comfortable gaming mouse on the market and performance is great too.
- Lachesis is nice, but the design doesn't suit me.
- Mamba is a bit pointless. With a cord, it's a Deathadder. Without one, it's just a wireless mouse with all the associated disadvantages.
- Rest is okay at best
Logitech:
- G500 is the G5's succesor. A brilliant succesor to a brilliant mouse, on par with its Razer competitors.
- MX518 is still a great budget gaming mouse
- G9x has a curious design, you should really try it out before buying. Great performance, certainly on par with Razer.
Also, take a look at Roccat. It has some very nice products too and costs about the same as competing Razer and Logitech mice.