i've run quantegy 407 and it really does compress nicely... like 408, it's made for portables like my uher (or a nagra), but with the 406 formula... i have mostly used it for live acoustic music and field recordings with consistently great results... i plan on experimenting with it to get rough mixes from the scully... and it may really sound nice on that little deck for comping drums and percussion... i will see... but... i don't think i would recommend it for mastering...
much of the choice depends on your genre and the ratio of soft passages to loud passages in your performances... print through is bad, but it really isn't nearly as obvious under a wall of guitars... so, older tape formulas might be alright... one gently played
acoustic guitar though, or a soft voice... and you will have a problem... signal to noise ratios are also more crucial on softer music than loud, but... alot of it also depends on whether you are trying to just splatter it on the tape for that once dreaded and now romanticized compression... or whether you want a very clear and warm sound with very little noise...
that 440 is a great machine... underrated, but then in audio that is a good thing... parts aren't hoarded like spanish coins... whatever tape you choose, whether it is a +6 -- which the machine was designed for -- or +9 -- which it can be adjusted to use -- you will need to get it biased and set-up for that formula... there are alot of options out there in one-pass, new old stock and newly manufactured tape, so shop around and find something you really like...
next time i see him, i'll ask my pal here in town who has a AG440C what he spins... what are the other ampex 440 owners in this forum rolling? c'mon fellers... chime in...