At your initial question:
None.
I've had the "luxury" to hear both
-HD's have bloated bass with no treble or mid-range
-Tours have no real bass extension
Now you want bass, here are some suggestions, and I see you are form the UK (finally someone) so:
Earphones:
-Sony MDR-EX510's = £45 = better lower extension and overall good mids
-FS Atrio MG7's = £70 (from the atrio.me deal from the US, or from these forums) - by far the best sub-bass kinds I have EVER heard
-TFTA 1XB & 1V = Ironically £50-60 from me selling them or £100 brand new = best mid-bass (1XB) i have ever heard
-Monster Turbines £30-50 = Bloated bass, but better than the tours
-Monster Turbine Pro Gold = £100-220 (depending on your place you buy them from) = great bass levels, overall really nice earphones - make sure you buy from an authorised dealer, or a person who can prove the original proof of purchase being from an authorised dealer, as there are A LOT of fakes around
-Monster Mile Davis Tribute = (Currently at £100-140 at monster US - get someone from the US to buy them for you) - i ain't heard them yet, but read GREAT things on them in comparison to the MTPG's (above) - so they should do very well...especially at this price point.
Headphones:
-Sony MDR-XB500's = £35-50 (amazing mid-bass, bit muddy sounding, but a HELL LOT better than the solos)
-Sony MDR-XB700's = £60-75 (all-round amazing headphones, only downside...they are huge...i wouldn't carry them around)
End of the day, you can buy whatever you want - but honestly, I wouldn't buy any of the beats, they are over-priced for what they offer.
They might sound good at first with their heavy emphasis on the mid-bass (impact of bass) but if you comapre them to real earphones or headphones, you will realise a lot of detail is not only lost, but the lows (bass) isn't as well pronounced/extended