It is on stackexchange that I read for the first time that there is a material difference between UK and USA visas. That difference being that while the US visa essentially only gives you permission to travel to the US border at which point you will be evaluated for entry into the USA, the UK visa aka entry clearance is one which already essentially gives you permission to enter the UK and that your interaction with immigration at the airport is mainly a formality.
Coming from a person who was a non visa national who previously had to apply for and was approved many UK and UK visas and visited both countries quite a bit, I find no material difference between the two as suggested. The questions I get at the UK airport from immigration officials is no different in depth from what I got at the US airport. I know anecdotally it is the same with friends of mine and virtually everyone I know personally who has visited both countries. Actually most of those people have asserted that UK airport immigration are tougher in their questioning.
Does anyone have access to data showing the percentage of people(preferably with visas) denied entry at USA borders vs those denied at UK borders to determine if that difference is statistically significant? Information like below would be somewhat helpful extrapolating the data required
My null hypothesis is that there is no significant difference in the proportion of people with visas denied entry to both countries and thus no material difference in the UK and USA visitor visa.
H0: p1 = p2
p1 = the proportion of denied entry arrivals for the USA, and
p2 = the proportion of denied entry arrivals for the UK.
This report implies I may be right and that for nationals of some countries, there is no difference.
The results of such a hypothesis test will be another data point in informing my decision whether to go for a UK entry clearance before my next visit.
Disclaimer: I am from a sub-Saharan developing country (as are most of the people I reference) which like most sub Saharan countries has a high incidence of visitors to developed countries not being true visitors, but people looking to emigrate.