Hi,here. Logically your thinking is correct. However - as has been pointed out - in BOTH cases, applicants need to satisfy the Entry Clearance Officer that theirs is a genuine relationship. So in that sense, chances of success are more or less eeksy~peeksy.
Financially, however, marrying in the Phils is a lot less expensive ... not least, in that it overrides the necessity to fork-outthe same amount twice within a comparatively short space of time ... because, no sooner has the fiance(e) arrived in the UK, than arrangements require to be made for (what is likely to turn out to be a much more costly wedding) to ensure that he/she marries within 6 months ... then afterwards apply for Further Leave to Remain.