CareerCup

hashtable is better as it adds/searches elements in O(1) time, provided hashfunction uses a good algorithm to distribute elements in different buckets.
In bst, add/search is of order O(logN) and in tree its O(n), whereas in hashtable its O(1), hence hashtable is better here.
In hashtable, we keep elements in array, hence we use extra space and thus in terms of space complexity, tree is better.

BST can perform operations like sorting in constant time as opposed to hash table

In addition to the points already made binary search trees can produce an ordered traversals of elements by key. Hash tables, on the other hand, do not inherently have this capability.

Tree Vs Hashes.
1.hashing cannot help in range queries.. while b trees or bst trees can help in range queries.
2.tree is a more compact and flexible when it comes to growing and shrinking in size. Hashing would waste a lot of space.
Hash Vs trees
1.tree does help in sorting but the use of map in c can also help in sorting.
2.Merging of two trees is difficult unless they are leftist trees( O(logn) merging), while merging two hashes is simpler.
3.insertion and deletion in tree logn , while the load factor governs the actual insertion or deletion time.