Wawrinka and Safin are similar in some ways. Both have incredible high peak levels, high enough to challenge peak/prime Federer, Nadal or Djokovic. Both are unpredictable/inconsistent, beating ATGs to win a slam one tournament, only to lose to challenger level players the next, frustrating as a fan of either. Both have Open Era Top 3 GOAT BHs (1 DHBH/1 SHBH), as well as similar career win/loss %. Both won similar number of ATP titles (15/16), and also made 4 slam finals and winning Davis Cup. Wawrinka won one more slam, but Safin makes it up with 4 more Masters titles, so achievement-wise, it's very similar.
Who has the better:
Serve - Safin
FH - Wawrinka
BH - Safin
Volleys - Safin
Overheads - Safin
Movement/footwork - Wawrinka (clay), Safin (HC), parity (grass)
Mental strength - Wawrinka
Some of their best tournaments:
Safin - A0 '05, Paris Bercy '02 (I think), USO '00, AO '02 (how he lost that final is tennis' biggest mystery) and WTF '04 (lost a tight SF to Fed which included a massive TB - had his chances to close out the 2nd set then it's anyone's guess who'll win in the 3rd - Hewitt would have been toast in the final either way).
Wawa - AO '14, RG '15, MC '14 and AO '13 (had his chances to close it out vs Djoker but choked, could have won the whole thing had he won that match).
Putting bias aside, I have to go with Safin as the greater of the two. Just watch the USO final 2000 how he dismantled Sampras, or any of his GOATing matches and you'll know were i'm coming from.
What are your thoughts?