Mightymogs

It's a tricky question with no right or wrong answer. In general when buying gold you are mainly reliant on the spot price rising to make money. There are exceptions when it comes to low mintage, desireable modern coins but even they can fall out of fashion. Generic gold will sell at a small premium over spot privately or less than spot commercially.
Historically silver coins can make larger gains and the spot price is not such a factor.
The big issue is when you come to sell. Are you selling a weight of precious metal or are you selling a collectable item ? If it's by weight then it's a coin toss as to whether gold or silver make better gains. If it's as a collectable item then silver has been shown to make better gains.
There are a lot of other commodities that could be better for long term investment but few that can satisfy that Scrooge McDuck feeling of owning something so desireable and shiny !
Think of it as wealth storage rather than an investment and you wont go far wrong...