I’ve done it from all 3 sides and the most brutal is from the south (Dinas Maddwy).
Last year I was feeling fit and arranged to meet the family at Lake Vyrnwy (from my in-laws, 12 miles away) and the plan was to do all 3 ascents. Thankfully I ran out of time (!) after 2 and missed out the Bala side.
Churned away on a 36/30: very hard work and came out of the saddle.
Such a beautiful climb and area; a tonic to busy Northern Snowdonia.