Taking any medical/efficacy questions out of the equation (I have never used gel) I would go for patches if you will be dealing with NHS repeat prescriptions, as at least they come in single units.
A patch is supposed to last half a week, however many GPs have the sense to realise that patients who are active and shower more than twice a week go through them more quickly.
Gel, or anything that comes as a liquid or in a tube, often tends to be prescribed in ridiculously small quantities and it can be a constant battle to obtain an adequate and reliable supply.
Also I would ask for your treatment to be prescribed generically where possible rather than brand names, then you are less likely to be left high and dry (bad pun sorry!) in the event of product shortages.
However in an ideal world if money and supply problems weren't an issue, estradot patches are hands down the best for size, absorption and adhesion.