Juvederm 4 Vs Sub Q ? Is 6ml of Sub Q Going to Give Me Better Results ? Based in UK

A common effect of aging is facial volume loss or deflation.  This is especially evident and occurs earlier in naturally thin people who enjoy exercise.  There are many ways to restore those plump high cheeks and midface that are a symbol of youth.  Fillers, such as Juvederm, Restylane, Radiesse and even Sculptra, will all accomplish this goal.  There are benefits and drawbacks of each:

Juvederm- very versatile, can be used in almost every location on the face including lips, around the eyes and in creases.  The effect lasts between 6 and 12 months.  It comes as a 1 cc syringe and costs about $550/syringe.

Restylane- similar to Juvederm in almost every aspect.  The cost and duration are about the same

Radiesse- can be used in many areas and provides excellent volumization, but CAN NOT be used in certain areas most notably in the lips.  It needs to be injected deep, so it won't correct creases and needs to be used cautiously around the eyes.  It lasts longer, 12-18 months, but is a little more expensive for a little larger volume ($600/1.5 cc syringe).

Scultpra- can only be used deep but provides excellent volume to the cheeks and midface.  Expensive ($1000/vial) but that gets you about 6 cc of volume depending how you mix it up.  It lasts years

Have you considered facial fat grafting?  For someone using 6 cc of Juvederm every 6 months, you seem to be the perfect candidate.  It is your own fat, usually harvested from the belly, flank or outer thighs. It is permanent.  There is something else to fat that seems to soften and freshen the skin overlying the area injected.  For adding generalized volume to the face it is absolutely the best.  

As long as the thicker type fillers are similar, the aesthetic results will be determined by the MD's ability to understand and follow the proper aesthetics of facial beauty...in this case how to shape the cheeks to their aesthetic ideal.