What way do you not see a difference? The sound? There is a difference. I remember when I heard I Luv U for the first time and remember thinking 'what genre is this
'. Everyone was calling it Garage but it didn't sound like it, I'd never heard anything like it tbh. Compare it to Shanks & Bigfoot's 'Sweet Like Chocolate', DJ Pied Piper 'Do U Really Like It'. Totally different. Around this time as well, journalists were using terms like '8 bar', and 'dark Garage' / 'grimy Garage' to describe the sound the production was taking. That's how the term 'Grime' became a thing.
Ninetails has it about right in this thread. Wiley (most people would say he is the biggest pioneer) was in Pay As You Go who were a Garage crew (check 'Champagne Dance'). He also produced 'Nicole's Groove' in the 90's under the name Phaze One which is clearly a Garage record, but sounds nothing like Eskimo or Ice Rink which are Grime. Megaman (of So Solid) was also one of Wiley's influences/mentors.
Pretty much all of the big boys and pioneers of the sound, were Garage heads before Grime became a thing. You can hear the Garage influence in producers like Royal-T, Preditah, Rapid and so on.
As for DnB, not too clued up on that, I've never really been a fan, but most of the yardie type MC's were junglists in the 90's. There is a track on Kano's first album called Reload It and you can hear the DnB influence on that.
I'd probably say Garage influenced the production more, and DnB the vocals, or rapping style if you like. Originally anyway.
http://www.youtube.com/watch?v=26jo6EA_tkU
Wiley in 1998.