IMO Modern Times was more rewarding of a campaign than the main one. They throw some silly challenges at you in MT which will throw your game off in a big way most of the time.
On the main campaign, they don't really do many extraordinary things designed to alter how you play (so, for example, if you wanted to always be a rum baron, in the main campaign, you're almost never discouraged from that, but in MT, there'll be many instances where that becomes a bad strategy [such as sugar prices falling out, or an island with high altitude unsuitable for sugar, or inability to build factories, or the Americans pressuring you for chemicals, etc.]).