Here are my stats for the Heart Grinder: $1000 - 26 times - 22% $750 - 26 times - 22% $500 - 36 times - 31% $250 - 29 times - 25% My guess is the actual odds are even for all four, and that I just got a but unlucky hitting $500 a few times. So for me the average payout was $604 per 20 hearts, but I bed the real average is closer to $625. So you are going to get about $30/heart with no XP. If you go the Train route*, you will get $1000 for 100 hearts (so just $10/heart), but will also get 100xp (or 1XP/heart). So, basically, you're trading $20 cash via grinder to get 1 XP via train route. Since you generally get 10% in XP per dollar spent when buying buildings and items, you are statistically better off to use the heart grinder, EVEN IF YOU ARE SEEKING XP, just take the extra cash you make and buy buildings/decorations for XP instead. *meaning, you buy choose-choose-choose-you trains for 100 hearts, and then sell them.