The 1878 Half Dollar has a slightly smaller mintage than many of its contemporaries yet it is still considered a "type" coin that garners no premium for additional scarcity. To my mind, that makes this date a good value compared to coins with larger mintages. This is not the last year of the design type, but it is the last year before mintages dropped off precipitously for the remainder of the series. Scores of Mint State examples exist, but they tend to be mid-range (MS63 or thereabouts). Gems are very scarce and any 1878 Half Dollar in MS66 is a condition-rarity.
The strike quality on this date is usually quite strong. Luster ranges from brilliant to frosty. This date is not known for being "baggy" but try to find coins that have nice surfaces.