"Tourists like cold season"
Translation:Watalii hupenda kipupwe
In terms of Swahili: The hu- tense kind of explicitly adds a bit of the meaning of "in general", "as a rule", "habitually" etc. The -na- tense generally indicates it's around now, potentially with a shorter time frame. There's a lot of overlap between the two.
In terms of this course: If it's in the hu- lesson, use hu-, elsewhere use -na- and if you're strengthening your skills and don't know what lesson the question comes from, just guess ... and report report report.