Indoor vs. Outdoor Tanning
The perpetual question of which tanning method is safest lingers, although there remains no clear cut answer. Strong arguments are presented on both sides, however.
In indoor tanning, most salons put a limit on how long you may stay in a bed or booth, thus reducing the likeliness of a burn. Many salons also prohibit patronizing the facilities in 2 consecutive days. Moreover, many beds now boast of UVA only bulbs. As you will remember, UVB's are the rays primarily responsible for the burn reaction in one's skin. By eliminating UVB rays, salons will say their beds are safer.
In outdoor tanning, the light you are receiving is natural - not produced by artificial means. Sunlight also one of the only sources of Vitamin D - an essential Vitamin needed to sustain life. Tanning salons do not.
Ultimately, while tanning, like almost anything, in moderation is not necessarily bad, it's your responsibility to protect your body. Limit your time in the sun. Remember, the best looking and most even tans are results of short but regular periods of sun exposure. And you should always wear some sort of protective lotion, clothing or eyewear to protect yourself.