The Akai is an S-arm mid-mass arm table, The Harman Kardon T40 is a straight low mass arm, as is the Dual. All are belt drive, the Harman is from the best period of Harman turntables....
My guess is the Harman is the best TT of the three.
They are very similar in technology, market segment, etc...
Really depends on your intentions, and your budget.
Do you have any idea of what type of cartridges you would want to try on your table?
If you are interested in MC cartridges (which are mostly lower compliance) then the Akai has the edge, as the heavier arm will match better.
If you are interested in MM high compliance cartridges, then the HK and Dual are better due to the low mass arms.
Budget MC cartridges of note: Denon Dl103, Benz Ace, Dynavector DV10x5
For an MC based setup, you will also need a phono stage that properly supports MC's (higher gain, appropriate loading)
MM/MI catridges - these are mostly high compliance with a couple of exceptions... examples: Shure V15, M97xE, Ortofon OM & 2M Series, Grado (any), Audio Technica AT120/440/150, Stanton 680 & 880 series, Pickering XV15 & XUV/XSV series etc...
Low compliance MM's that would suit the Akai would include: Audio Technica AT95, Ortofon Omega, most Nagaoka's
Many of the MM cartridges can be upgraded by ugrading the stylus fitted - if the turntables come with a cartridge already fitted, you might decide partly based on the fitted cartridge (if something really nice and suitable is already fitted, then for the price of the stylus you would have an excellent setup)
more food for thought?
Bye for now
David