The phrase "arguably even more impressive" is correct and usable in written English.
It can be used when you want to suggest that something may be considered more impressive than another thing, but this is open to interpretation or debate.
Example: "The first film was a masterpiece, but the sequel is arguably even more impressive in its storytelling and character development."
Alternatives: "possibly even more remarkable" or "potentially more outstanding".
A top-four finish is arguably even more impressive.
Oh, and an arguably even more impressive feat was getting Raphael Saadiq to compose the score.
DiMaggio's ratio of home runs to strikeouts is arguably even more impressive than his 56-game hitting streak.
Six penalties from six attempts took him through the 500-point barrier in the tournament but the deftness of his handling and shrewdness of his option-taking were arguably even more impressive.
Debussy's victory in the Arlington Million on yesterday was arguably even more impressive, given the way the four-year-old lost at least half a dozen lengths when trapped behind runners on the home turn and had to come from an impossible-looking position to pick up home favourite Gio Ponti in the final strides.
Others pointed out that Bradley Wiggins received 492,064 votes in the 2012 Sports Personality Awards – the most ever – after his Tour de France and Olympic gold medal double, while Chris Froome, who was arguably even more impressive in winning the Tour, only managed sixth with 37,343 votes.
But the expansion of power driven by natural gas has arguably been even more impressive.
Griffin may have the highlight reel runs and the showy statistics, but Luck has arguably been even more impressive under considerably more challenging circumstances.
Arguably, the download figure is an even more impressive figure than the oft-referred 100,000 apps because it shows how many applications people are using and how many mobile transactions are taking place.
The angiosperm diversity of Australia's Southwest Botanical Province SWBPP: Figure 1) is also very impressive (>7300 plant species and 49% endemicity [ 2]), and is arguably even more intriguing than that of the Cape, because this region has very limited topographic variation.
Arguably, even more so than The Beatles.
