You want to get healthy and get into tea. But which tea is better to drink? Green tea or Black Tea?
First - what are the differences?
Black Tea comes from the camellia sinensis plant. The exact same plant as green tea. The difference? Oxidation! The same process that turns an apple brown, or rusts your car. This is often confused with fermentation. True fermentation means there is some microbial process taking place - such as sauerkraut. For the most part, Pu-erh tea is the only type of tea that undergoes true fermentation.
Green tea comes from the same plant. The only difference is that it is steamed or pan-fired before oxidation can take place.
Regardless of the color, all teas have health benefits. And even though there aren't going to be clinical studies that offer definitive proof, there really isn't a downside to drinking tea. 
A few people may argue the above, but lets be clear, we are not talking about drinking five gallons a day. Moderate tea consumption taken without sugar will have benefits provided it is combined with other healthy habits. These healthy habits combined tend to lead to a longer and higher quality life. If you google 'blue zones' you'll find a lot of evidence that drinking tea is a habit shared by many centenarians, be it from the Greek Isles to Okinawa, Japan.
The main difference between green and black tea are the percentage of anti-oxidants.
Green tea has higher levels of catechins - these are the class of anti-oxidants that tend to ward off chronic diseases and cancer.
Black tea has theaflavins and thearubigins which may benefit your cardiovascular system.
If you had cancer, or are want some insurance against it - drinking green tea may help. Will it cure cancer? No. Is it guaranteed to prevent it? No. But it will better your odds assuming you don't eat cinnamon rolls for breakfast, McDonald's for lunch and Taco Bell for dinner. To be clear, the FDA allows the language 'may reduce the risk of breast and prostate cancer', which has been effect since 2012. In fact, a tea company fought the FDA and won regarding using this language. 
But the phrase - 'which one is healthier' is like asking is a banana or an orange healthier? They both have their own benefits. Our advice, if cancer prevention is your goal, or maybe you have cancer that runs in the family, a bias towards green tea wouldn't hurt. 
All tea is good.
But for overall health, why not drink both. Or try a green/black blend. Think of eating like investing in the stock market. Do you invest in only one or two stocks? NO! Same for diet. A well BALANCED diet using a common sense approach where you do not overdo one category of food, and tweak based on your body type.  As for drinking tea - a basket of good quality tea is all you need. If you are new to tea, drinking black in the morning, green/oolong in the afternoon and herbal at night is a great way to incorporate tea.