As mythic rares, these cards are going to be difficult to pack anyway, but these variants are likely to be highly sought after once the set launches, not just for the value a complete set of the elder dragon cards may hold, but also for their eligibility as Commanders
Ugin, meanwhile, isnt always asymmetrical, but can often be so, either because youre playing a lot of artifacts and colorless spells, or because youre sequencing up to casting him and not dropping too many resources into play
Games of EDH are rarely decided by small reachers blocking small fliers, so you can do better
If you counter their creatures, not only will they be unable to attack with them, but your opponent will lose the element of surprised and be forced to play more cautiously