Oh dear, this eternal question...
I had this same debate in New Leaf, and since I couldn't decide, I went for both. Loved them to death, but in the end, I ended up loving Beau a tiny bit more. Both of them are very well designed, but there's just something special about Beau... maybe it's because we're both Aries so I'm biased lol.
In NL I liked Erik's house interior a lot more than Beau's, but I don't really like how it looks in NH, so I settled for Beau. Luckily my boyfriend has Erik in his island so I can pay him a visit anytime I want <3