Either one of the choices will be powerful and impact your game
Also, as a last resort, you could even Tribute Summon Earth Armor Ninja
To prevent scalping of first-edition cards, it is impossible to tell if a card is a reprint, unless it has been errata'd and had its text changed between printings
While this may not be a Tier 1 strategy, Swans of Bryn Argoll have inspired players to craft combo-centric Modern decks leveraging it alongside Seismic Assault
Thunderous Snapper, on the other hand, might not be as desirable to GU magessure, its a four mana 4/4 that can be a card draw engine, but some GU decks will want to stretch their manabases quite substantially, making this turtle hydra too hard to cast