I'll share my thoughts about this.
I tried Forge, but I saw it crash a bit too many times (of course I always reported the crashes on the forum). If I mod DotP, it's very likely that a correctly coded card won't cause crashes due to an engine problem, which is quite a relief. I also found Forge somehow slow, but this is not a problem of Forge, it depends on me: being used to DotP which stops as few times as possible, 100% rule-compliant implementations where the priority passes back and forth and waits for my "OK" to be passed start to annoy me very soon. In DotP we don't get to stop at the upkeep unless there's a triggered ability to answer to, which is a big downside, however I still consider a fast game more important than that.
Another good idea on DotP is badges: the most common abilities (flying, trample, haste, etc.) cause a small icon to appear on the card, so I don't need to re-read the cards everytime I attack in order to know if that particular card will be able to block me. Moreover, if I get one of those common abilities "until end of turn" because of another ability that granted it, I'm always kept informed about that.
Finally, just 2 words: "eye candy"! DotP is pretty to see, with all the 3D and the fancy animations and the cards that seem real paper cards. This shouldn't matter much in a card game, but it's pleasant, you can't deny it. In Italian we say
"anche l'occhio vuole la sua parte" which has no literal equivalent in English but it basically means "appearance might be unimportant, but if it's good, it's always well accepted".
![Very Happy :D](./images/smilies/icon_biggrin.gif)