The SE is a great phone but there is a lot of differences between it and the 7. The 7 is just superior in every facet possible except for screen size which is a subjective feature.
iPhone SE advantages over iPhone 7 series:
Screen size (subjective opinion)
Built-in headphone socket (objectively true)
Cheaper (objectively true)
Flush camera, no bulge (objectively true)
Total size and lower weight make it more mobile, fits in smaller pockets (objectively true)
Nicer form factor (subjective opinion)
Round volume buttons, top position for power button (subjective opinion)
iPhone 7 series advantages over iPhone SE:
Screen Size (subjective opinion)*
Better display (objectively true)*
Faster Touch ID (objectively true)*
Force Touch (objectively true)*
Better cameras (objectively true)
Jet and matte black colour and finish -
options- (objectively true)
Has barometer functionality (objectively true)*
Higher storage capacity options (objectively true)
Nicer form factor (subjective opinion)*
Flatter, longer volume buttons, side position for power button (subjective opinion)*
So yes, there are some big differences, but I don't think it's true to say the 7 is superior in 'every facet possible except screen size'. I asterisked the features in the 7 I don't care about enough to matter to me personally, which leaves the camera (a better camera is always better) and black options (nice but I put my SE in black case so that was borderline for the asterisk...!), and the only thing I
really really wish for is that the 7-series iPhones have higher storage options.
Overall I don't regret my SE purchase at all, and I honestly wouldn't swap it for a fully loaded iPhone 7 Plus (other than to sell it and buy another SE and pocket the change, to be realistic!).