i recently switched from a h50 to a D14, so hopefully I can give you a little insight.
The D14 far outperforms the h50 in my system but from reading around the h70 seems to be on a even par using the stock fans, so its just a case of what suits you more.
The D14 is quieter, cheaper and more reliable (although you cant really use that as an argument).
But its pretty huge, and only really works best when you have a decent airflow running through your pc, so if those are 2 things that concern you then go with the h70.
For me personally I'd go with the D14, I'd rather pay less money and have a quieter system. Also its not actually that heavy in my opinion it looks pretty garish when you get it out the box but its surprisingly light which sort of removed all my concerns about a huge heatsink hanging off the mainboard.