When we first planned to get guinea pigs they were definitely going to live outside.
We even bought a very large and well insulated hutch with cover, etc.
But the piggies came home during a cold snap and were absolutely tiny, so they moved indoors 'temporarily' until the weather improved.
Based on this I would say the advantages of having our piggies indoors include:
- Being sure that the ambient temperature is never to extreme for them
- Having almost continual interaction with them because we are constantly going past their cage
- Quick bonding because even when we don't have time to get them out into their run we can just give them a quick pat or a small piece of something yummy
- Having them really feel like part of them family because it is easy to pop them out for lap time when we are watching tv without having to worry about moving them between extremes of temperature
- Literally having the kids pend hours just sitting watching them without having to consider what the weather outside is doing
- It is super easy to keep a visual check on their health and well being because we always hear strange noises immediately, can see when a food bowl is empty, etc
- Not having to worry about predators (we live in a rural area with cats, foxes and martens)
The downsides to having them indoors would have to be:
- The space their hutch takes up in our main living area
- The mess (think hay everywhere, on every floor of the house)
- The smell (the outdoor hutch is not designed to be used long term indoors without a full weekly wash down)
- And occasionally the noise (full blown wheeking at 6 am on a Sunday anyone?)
But basically I think different set ups work for different people, and it is a matter of doing what best fits your lifestyle whilst keeping your guinea pigs safe and healthy.