Need to dry...
Of course you save space having a combo (=lavasciuga), and you save time not unloading washer/loading dryer... Don't know if you save energy, running a separate dryer I think is cheaper than running a combo drying...parcitularly if in your combo you cannot dry the entire washed laundry.
If you add the consume (KWh) of the dryer and the washer, you get a result different from that one of the combos, but it refers to the entire cycle, why the combo consume referes to the WASH AND DRY cycle wich is HALF LOAD!!!
Here is VERY recent (2005) the Candy Alisè 5+5 (Kg), which can wash and dry the entire full load at once, the only that has the same drying capacity as the drying one (really wrinkless laundry?!?!? I'm scettic...). No combos I know can do that...the standard is 5w-2.5d, or some other as 6w-3d (Zoppas), 7w-3.5d (Hoover), 6w-4d (Indesit)...drying capacity is always less than washing one.
Thus, to take the best advantages of a combos I think that you should to be able to wash and dry the same maximum capacity, dont' know about the LG combos, but I think the drum is quite big enoough to do that...
Remeber then, that generally combos run condesing WATER COOLING dry system, different from any othe condensing dry system of a condensing dryer which is AIR cooling, that's why a combo uses such awful amount of water to run...
However, what a beautiful confort of the modernity to put the dirty laundry in a "box" after dinner and wake up in the morning with all washed and dried

))
GoodBye
Diomede