My opinion for both is that GNXIV has really good beam weapons and melee, but the heavy downside to that is that it only has beam range weapons, if you face things that have I-field or MA, you won't have a good time.
Unicorn is fun and all, melee is quick but the range is not as far as GNXIV. The beam magnum is a wonderful weapon and the zook it has is good for dealing with MA.
Overall, you can go for GNXIV cause it has alot of good points and is a very modern day suit in SDGO, but I rather get Unicorn because it's more of a multipurpose suit.
SDGO: TW: Quantj KR: Rias NA: Quant
Elsword: NA: Edaina KR: Melodiana, Jillian
Current Interest: Puzzle and Dragons