for me, UH is simply better all around. an on-demand CC (asphyxiate & gnaw), extra survival CD (corpse shield), 15% aoe dmg reduction (good vs DH dmg) and NECROTIC strike pressure.
frost lost a lot of pressure vs healers without auto-crit frost strikes, icy touch purges and necrotic strikes. they are also still very squishy, esp vs melee cleaves (which is predominant atm).
play what you like in the end. i loved frost, but after playing UH for a few weeks. it seems pretty fun with the festering wounds gameplay. ie. necro vs ss depending on the situation.