I must admit I’m not very familiar with Android. I think it can be more unsafe for ”regular” users since it’s possible to install applications outside of Google Play.
I prefer major certificate authorities. Symantec, Thawte, RapidSSL, GeoTrust, AlphaSSL, Comodo etc are some of the finest CAs in all over the world. from the price view you can find pocket pleasing price at www.ssl2buy.com