Sometimes, companies offer the same beer in bottles and in cans. Everything else being equal, should I go for the bottle or the can? I know that e.g. Guinness have their "floating widget" in their cans that releases nitrogen when you open it, but assume that this isn't the case.
In particular, I'm looking for the effects the inner coating/material of cans has on beer.
A modern canned beer should never taste like metal. If it does, you're probably drinking straight from the can, and while the folks at The Alchemist might recommend that, I can't say I share their view.
Modern beer cans are lined with a water-based chemical that essentially ensures that your beer never touches metal. This in turn means that strictly speaking, canned beers will keep longer without being skunked, and pressurized packing means there's less air in a can then a bottle, which adds further preservative benefits.
That said, very few beers that are good enough for this decision to matter are offered in a choice of containers - most small breweries just don't have the capacity to both can and bottle - especially of the sort of small-batch stuff that you'd actually be interested in trying to cellar and age. Furthermore, there are significant environmental and economic arguments in favor of both bottles and cans.
At the end of the day, choose the packaging that's more convenient for you to store, consume from, and recycle when you're done. The quality difference is essentially insignificant.
As you might expect, cans can impart a metallic flavor on some beer, but on the flip-side, they are much less prone to skunking. So if you're looking to store the beer for a while in a cool, dark place, I'd say bottle. However, if you plan on keeping it in a light place or outdoors, a can is probably your best bet.
I'd strongly dissuade anyone from ever drinking anything from an aluminum can, not just beer. As mentioned by LessPop_MoreFizz, beer cans are lined with a compound that attempts to prevent contact with the aluminum... That chemical, however, is Bisphenol A which is a potentially very dangerous chemical compound for your body when ingested...
CDC still says the chemical's health effects are unclear, research on chronic exposure has linked it to high blood pressure and heart rate issues. https://www.usatoday.com/story/news/nation/2014/12/14/bottle-chemical-bpa-health-newser/20397547/
Depending on who you ask, one will get a variety of answers:
...has also become associated with a range of ailments, including cancer, reproductive trouble, and irregular brain development in kids. BPA is well established as an endocrine-disrupting chemical, meaning that it likely causes hormonal damage at extremely low levels. The question is whether we get enough of it in beer (and other canned goods) to cause harm. https://www.motherjones.com/food/2015/02/no-i-cant-why-im-turning-away-canned-craft-beer/
And this:
BPA, in small doses, has been linked to obesity, early onset of puberty, diabetes, heart disease, reduced penis size, growth of male breasts, and even mean girls. https://www.treehugger.com/health/who-cares-about-bpa-canned-beer-more-popular-ever.html
Also, let's hope that it is true that this compound prevents leaching of aluminum into beer considering aluminum is one of the most toxic heavy metals for the human body.
That said, if you don't really care about a little thing called "Your Health," then there are several pragmatic reasons for why aluminum is good for beer storage:
1.)Aluminum blocks light and oxygen from entering the beer itself
2.)Cans are generally lighter and smaller than bottles, making them easier to carry and store
3.)Cans can allow beer to become colder more quickly
While the argument that beer spoils more quickly in bottles is accurate, who is letting the beer sit around long enough for that to happen?? Not I...
Also, while cans become colder quicker, they also become warmer more quickly when exposed to heat. Whereas, bottles will remain colder for much longer...
Finally, the taste issue - minimal research in your favorite search engine will show you that it is a 50/50 debate... some folks say it tastes like metal, some don't. This debate is non-existant when drinking from bottles, however...
With Guinness in particular, I always prefer the taste from bottle over that of the can... so in conclusion, ymmv but make it a bottle for me.
