Question
I am looking to plant a cedar as hedge coverage and was wondering if these are the same tree.  If not which would be the better choice?

thanks in advance

Answer
One of the varities of Thuja occidentalis is emerald green.  
Thuja occidentalis 'Smaragd' (also known as 'Emerald' or 'Emerald Green') - rapidly becoming the most popular cultivar, a relatively new introduction having emerald green foliage that retains its vibrant green color throughout the Winter, with very dense foliage held in somewhat short vertical scalloped sprays, narrowly pyramidal to columnar in growth habit, to 12' tall by 3' wide
I prefer the Thuja (standishii x plicata) 'Green Giant' or itis just called green giant. Green Giant : The Arborvitae Green Giant, 'Thuja plicata 'Green Giant', is a giant arborvitae that has bright green, fern-like foliage. This plant is very adaptable to wet or dry soils. The Green Giant is fast growing for an arborvitae and it is also very dense and they are used extensively for borders, screens, windbreaks or as an accent tree. When used as a hedge, the Green Gianat can be trimmed and kept to a dense 6 foot hedge.