There are a lot of good fullrange designs. Best is sort of up to you to decide and on what criteria. Flat response with frequency, or lively dynamics with subtle mid range emphasis, etc. If it sounds best to you, that’s what’s important. Having said that, it has been shown by studies that a neutral flat frequency response plays most musical genres equally well.
Some very good neutral flat response full range drivers include the TC9FD, 10F, B80, 3FE25, TG9FD, SB65WBAC25-4, FR58EX, FR88, RS100, and many more.
Combine these with a woofer and a low crossover around 300Hz to 600Hz and you have a great sounding system that can’t be beat for realism of small ensembles or girl/guitar stuff.
My main speaker for 4 years now has been the 10F/RS225 combo. I have built a lot of speakers and this one stands the test of time.
More info in my thread:
10F/8424 & RS225-8 FAST / WAW Ref Monitor
Not as neutral but very engaging and musical is the 0.53x Karlsonator. Using dual 3FE25 or dual TC9FD works great:
Mini Karlsonator (0.53X) with Dual TC9FD's