Hoo boy. Couple of things to address here.
Ooohh. Such a retort. Where'd you get your opinion that Cu is on par with Artoria and Herc? Is it from Rin's impression that Saber summoned by Shirou is stronger, or Kirei assessing that Cu is weaker? Can't argue it's because of Kirei. Shirou is worse, lowering all of Saber's stats whereas Cu's stats are consistent, and Saber didn't have Avalon at the moment. Or could you be referring to Nasu throwing Cu a bone by giving him the ability to bypass God Hand through rune BS and still calling it an uphill battle?
Also, to the other users. Both EMIYA's statements and Achilles accolades are not mutually exclusive. EMIYA assertions were about lancers in general, which could just mean that Cu's way above the average lancer in speed, not the fastest ever. There's no need to downplay EMIYA's judgement to address this point, and it's a stupid point to argue once you consider his arsenal must, by sheer numbers, be close to Gilgamesh's in scale, and he can read their history and actively search through them. At worst, EMIYA judged Cu from all the hundreds if not thousands of lancers he has intel on, and Achilles's spear might not be in UBW. The only reason why I myself ever brought up EMIYA's skill statement for Cu is because said statement got repeated, which narratively indicates it wasn't a throwaway statement. Also, regardless of what your opinion is of EMIYA's strength, his skills and judgement are consistently praised. So this was an illogical, and unnecessary approach to the debate.
I love how people bring up Mash as if that means shit. Did everyone just conveniently skip over the dialogue where Salter said she was weakened an held back? Teardrop photon ray is, at best, equal to Excalibur Morgan, but Mash was sure she wouldn't be able to handle it. Also, in London, she states that Modred's training session had the most powerful attacks she dealt with since caster Cu. Yes.......... everything she blocked up until that point was weaker than Wicker Man. Do not bring up Excalibur Morgan VS Lord Chaldea to prove your point.