In owning Port Royale (original) and enjoying it a lot, I decided to buy Port Royale 2.
Whilst PR2 has much better control mechanisims and overall a much more fluid and easier to control gameset, PR1 looks better graphics wise as it is able to be run at a higher graphics setting within the game. PR1 has a graphics control menu that is far more customiseable than PR2, and anyone interested in puchasing this game needs to consider the drop in graphics- especially if youre a running a relatively modern computer.
I have a 21" monitor and native setting is 1600x1200. The game at this setting looks noticeably worse than PR1, however general gameplay is much more enjoyable. It's still definitely worth purchasing, but just be aware of its graphics shortfall on higher specced machines to avoid initial disappointment.
Also, make sure you have up to date nvidia graphics drivers if you happen to be running 2 graphics cards in SLI mode, as I initially had display issues seeing world map. Overall a great game... and a terrific tutorial for those who havent played the original (or have and need a refresher).