I like the more adult and political themes of GOT more than LOTR because they are more contemporary - in line with the times so to speak. The characters in GOT are more complex than any single character in LOTR. Also plot wise, GOT is far more intricate and interesting to me, unlike the straight good versus evil plot of LOTR. (If you go deeper though, LOTR is really about anti-industrialization).
As books, I far enjoyed ASOIAF (GOT) more as well, as I found LOTR too wordy. GRRM's writing style is more efficient at telling a story, and more modern. As writers though, I believe JRRT is the better one especially in terms of prose and poetry. LOTR is a classic and is standard reading material in most Western high schools, something GOT will never be. GRRM copied JRRT's style of having a world map (Middle Earth vs Westeros/Essos) with thousands of years of history and strange and varied cultures and dialects. LOTR is more impressive in this regard.