Jan-May is when Burundi and Rwanda are the only fresh crop coffees so at times you'll see these appear. They're a bit smaller so you don't see them as often so in some ways both go unlooked.
You can expect a bit more a berry and winey type of coffee. Not the berry bomb like how Ethiopia does but a more fruit juice type. There's a slight herbal tone but nothing Sumatra like. If you've been tiring of the quality of Ethiopia's this is a solid one to check out.