Hi Kevin,
Good question.
The tsugaru shamisen is basically bigger than the nagauta, which gives a different (not better or worse, just different) tone from nagauta. So except for the larger size, the shape is the same, and they have the same things on them (doukake, koma, ito, etc). The Level 1 shamisen has a plastic skin, and I assume your nagauta shamisen has a natural skin. Does it? (natural skin has tiny pores, whereas plastic skin is completely smooth)
The Level 1 shamisen is fine IF you don’t already have a shamisen. But since you have a shamisen (I assume with a natural skin?), I would suggest playing that and save your money for a flexible bachi. That really makes the playing experience more enjoyable, imho.
If you ever decide to invest in a tsugaru shamisen, I recommend getting one with a natural skin, because then you get the best sound quality from your shamisen. 