For a shore excursion in Halifax we chose Peggy's Cove Fishing Village Tour. A beautiful spot on the coast with a light house and small village and great scenery. It was an hour ride before reaching Peggy's Cove, Once we arrived at Peggy's Cove, we were "allowed" a 30 min stop. Just enough time to use the rest rooms, snap a few photo's and back on the darn bus. When we arrived back at the peir, we hailed a cab and were able to see the Citadel, a fort that sits at the top of the city of Halifax. When speaking with the cab driver, he informed us he could have taken us out to Pegy's Cove for less than the Ships excursion - $42 ea adult, given us a city tour on the way and spent time at the lighthouse at our leisure. We've learned our lesson and will now venture out on our own more often.
We ran into basically the same thing in St. John's , New Brunswick. took the St Martin's tour, and found ourselves on a bus for about an hour with little stops along the way. Always 10 to 30 min allowed.
It really depends on what you prefer, we did not like the time restrictions and the crowded bus rides. The two cities were pleasant and if you like shopping offered quite a variety of shops. The floral gardens are nice at St. Johns, and we were told that the Reversing River Falls are impresive but bus tour did not hit it at the right time of tide when we stopped.
Hope this helps,