They're honestly built around a market of people who don't feel like fooling with mods (and I count myself among those who generally avoid mods for most games). I think the new NPC and quest content that Beamdog added is fun, although The Black Pits (a kind of arena mode) feels pretty superfluous in both games. The other nice thing about the EEs is that they include all expansion content for the BG series. Icewind Dale does too, but I would have liked to have seen them throw IWD II into that package as well. Of the three, BGII is easiest to recommend. I haven't played the IWD EE version yet (I just bought it today too), but it was much more combat-oriented than the BG series, which really isn't the most interesting part of these games for me.
I haven't played Siege of Dragonspear, which hasn't dipped below $17 unless you count that BundleStars package, which was really only of value if you didn't have ANY of the Beamdog remakes, but the reviews were mostly negative. There were some complaints about heavy-handed and unsubtle left-wing political messages in that expansion, but I'd be willing to check it out if it ever hit a $10 pricepoint.
EDIT: After 169 hours and 5 months, I'm finally "finished" with The Witcher 3, including both expansions. What an amazing game. CD Projekt RED really lived up to the hype on this one.