So I'll share a students perspective. I had a long solo X- country planned and I used the online service to file the flight plan. No issues since I'm pretty tech savvy, I also use their open/close by text option and updates via text for TFRs, weather etc. Got a full brief and printed out the info and headed to the plane. Before I made it I got a text about a weather alert. Mind you it's blue skies and METERs showed less than 5kts wind. So I called, the gentleman was very nice and explained the warning was for moderate turbulence at flight level 30-45. Mind you I filed for 2500', he laughed and said the automated service just sends those out because it was issued in the area. He asked if I needed anything else, looked and made sure I was OK the rest of the way and that was it.
I opened my flight plan when I taxied to the hold short line put the parking break on and before run-up. I flew the trip but it was slower than expected because I had some traffic in the pattern at one of my stops. I closed the flight plan after I parked the plane and secured it, in hindsight, I should have closed it when I hit the ground. About 10 minutes later the phone rings and it's flight services checking to see if I'm OK because I was considered overdue. Literally, as I'm taking to the briefer my plan closed and everything was fine, the time tag she said was 10 minutes prior. Their computers have a good 5-10 minute lag, or it took that long for my close request to reach them from my phone.
Moral of this very long story, I'm going to use both, the folks are very nice and the computer version is very through.