If you only intend to use it as an altimeter you will be fine, regardless of your choice, you could safe some money with the viso 2 though.
But if you want to use it also as a logbook (which I would highly recommend when going serious under canopy), that allows you to analyse every single second of your jump and canopyflight via some fancy graphs and cool tools, there`s no way round the n3. Because of its usb-interface its pretty easy to get your jumpdata analysed and printed on the screen.
Only disadvantage I could consider with the n3 beside its price: Viso battery life seems to last forever for me. And because I got kinda used to this I tend to forget to recharge my n3 prior to the weekend and have to recharge it via our dropzone-computer. Just takes an hour ore two to get fully loaded and wasn`t an issue ever. Not that it wouldn`t work with only 1/4 battery capacity but I like to have it fully loaded ;) just to make sure, I don`t have to think about it anymore during the weekend =)