There aren't really pros and cons to each method. Percentages are far more precise and therefore much more useful. However, the two are used for different things. Ratios are used as a shorthand way to work out the pot odds you're getting, so that you can work out how much equity you need in order to make a good call based on those odds. E.g. Pot odds of 2:1 means you need at least 33% equity.

In terms of learning to use percentages, generally a good rule is '2% per out per street'. So if you have 10 outs on the flop, you have 10 outs x 2% x 2 streets remaining = 40% equity. This is very approximate (probably only accurate to the nearest 2-3%), and you can usually add or subtract 1-2% based on blockers or backdoor outs.