Don' t buy either new unless you absolutely need a bespoke gun - Spanish guns have experienced a lot of price inflation recently for various reasons, and an equivalent used gun in 99% condition may cost 30-40% less.
What is your budget - that will affect the answer to some degree. Also, there are a lot of Arrietas out there with Orvis or G&H markings. Often, those guns go for less even though they came from the same factory.
I agree completely, your dollar will go much farther in the used market on spanish guns. Further if you find the prefect gun you long for is not the custom one you paid top dollar for, the used gun will sell at a much lower loss. I look at gun buys as rentals. The rent on a used gun is less than new by a huge delta.
Don't focus on name in the used market, focus on the individual gun, its quality, its features. All the big spanish names make some good examples and a few not so good. Consider a Older good condition Belgian or Italian gun as there can be some great values there if you are buying the gun and not the name.
