I would say that it's easiest to be a collector for Genesis, than Turbo/PCE... but people on this community would probably say that the quality of games on the Turbo rival the Genesis/MD library any day.
Still it's a choice that takes into account both practicality, cost and overall preference.
*worth noting though, that although carts for MD and Genesis are easier to find (eBay is not too bad with loose Sega carts) than Hucards, if you want to move into CD-based media, the problems (& costs) arise for both.