Fairy Tail: Sub or Dub?
Funimation's English leads stayed the same across all three Fairy Tail series. The checked casts, what ANN's critic said about the dub script, and how to compare.
Either track will carry you through all three Fairy Tail television series with the same lead voices, which matters in a show this long. Choose English if Natsu's energy is what you came for; ANN's Carlo Santos singled out Todd Haberkorn's "all-star performance." Choose Japanese if you want the original script without the English adaptation's ad-libs. Santos gave the dubbed and subtitled versions the same overall grade.
Who plays whom?
ANN credits Tetsuya Kakihara as Natsu Dragneel, Aya Hirano as Lucy Heartfilia, Yūichi Nakamura as Gray Fullbuster, Sayaka Ōhara as Erza Scarlet, Rie Kugimiya as Happy and Satomi Satō as Wendy in Japanese. The English cast it lists is Todd Haberkorn as Natsu, Cherami Leigh as Lucy, Newton Pittman as Gray, Colleen Clinkenbeard as Erza, Tia Ballard as Happy and Brittney Karbowski as Wendy.
Those names recur in ANN's entries for the 2009 series (175 episodes, A-1 Pictures and Satelight), the 2014 series (102 episodes, A-1 Pictures and Bridge) and the 2018 final series, so neither track swaps its leads between series. ANN lists FUNimation Entertainment as licensor of all three. The English ADR director changes once: ANN credits Tyler Walker on the 2009 and 2014 series and Kyle Phillips on the final series.
The 2009 entry also credits a separate English dub made for Animax, with Bianca Arambulo as Lucy. That is not the Funimation version, and this page does not compare it.
What the dub changes
Reviewing the first Blu-ray and DVD set in December 2011, Santos wrote that "the dubbed script takes various liberties from the original translation, but keeps the meaning intact." In his account most changes fit the pace of spoken English, and in comic scenes the actors add "ad-libs to add more humor." He also praised Tia Ballard's Happy as "an entertaining diversion." His review gives the dubbed and subtitled versions the same overall grade, C+, so his grades do not separate them.
That review covers the opening episodes only. It is one critic's view of one set, not a verdict on the whole run, and it describes the English script's approach without listing specific changed lines, so this page does not attribute any particular line to either track.
A fair way to compare
Pick one comic scene with Happy and one fight where Natsu is shouting, and hear both in each language. The comic scene is where Santos found the English script adding jokes; the fight shows whether the energy he praised in Haberkorn suits you better than Kakihara's. Then commit, because switching tracks partway through 328 episodes, the total of ANN's three entries, is harder than choosing once.
Use the Fairy Tail watch order for the three series, Fairy Tail Zero and the films, the Fairy Tail filler list for the arcs you can skip in either language, our checked Fairy Tail quotes, and the manga if you want Hiro Mashima's own pacing.