For the most part, that's up to you and what you prefer. Both types work very well and have good and not so good features about them. A transparent skirt on your dive mask can help if you have some level of claustrophobia. Being able to at least somewhat look through the skirt provides a more open feel and does increase your peripheral vision. This can be helpful in any case if you are in darker environments or murky water. A colored, usually black, skirt, on the other hand, can help with reducing glare. If you dive a lot in shallow, sunny waters then the glare from the sunlight can get distracting and annoying. Most underwater photographers use a dark skirt to eliminate any glare while taking pictures.