Well, no, I think the difference is in blitz you only get a few minutes and in a simul you get a lot more time.
Also a master and a GM is very different 
Which is better to play vs Master 3 min or simul
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I'd want to play him in a simul. It's a feeling I've never had before. As I've played many blitz games here on chess.com.
Dec 28, 2015
0
#4
" in a simul he plays 19 other people and most likely wont remember your game."
Not True.
About 25 years ago, I watched former GM Walter Browne give a 40 Board simul in Toms River, New Jersey. The rule ( as typical of simuls) was the players had to wait for Browne to show up at their Board before making their move. This way, the exhibitor sees your move, then thinks and makes his move. When Browne got to this one Board, a player made his move and Browne immediately said, "no, that's 2 moves !" The fellow immediately said "no, this is my move". Browne said "no" and proceeded to rapidly put back the pieces to a position about 5 moves before , saying. "this was our position", the guy acknowledged. Then Browne said and moved the pieces very quickly -- I played here, then you played here -- doing that for about 5 moves. Then finally said, this is the position, now what do you play ?
I was amazed, as the opponent then played his move.
In answer to your question, your chances are much better off, as others stated for the GM to play multiple games rather than just 1 against you.
Dec 28, 2015
0
#5
No im talking abou online, not OTB. OTB there is no clock and Master can spent if he likes 2 minutes for a move or more at any board. The thing is in fide online arena server every other day there is master challenge blitz or simul you can join. But i noticed masters in simul they does not spent more than few seconds and they make bad moves sometimes. Few people managed to win or draw including me, while in blitz session is way harder to snatch a win. Only at end in simul , where only 3-4 boards are left and master time has increased due to inc each move only then they spent more time and play strong. But thats not true experience for me, maybe for a lower rated player. I prefer and i do think is way more prestigious to play 1vs1 vs Master in blitz than online simul (otb i will prefer simul) - having 30 min or so for you to think and watching how the master come, spent 5 seconds and go away not good. They are more focus and serious in blitz single game.
Hi Everyone. If you can choose what you will pick and why:
To play 1 game quick blitz game vs a GM OR
To join 20 players in a simul vs a GM. But the master roughly will spent same average time for each move as he will do in blitz game vs you. In other words he will think just for seconds each move but the difference is - in the blitz he will be focused whole game just that game, in a simul he plays 19 other people and most likely wont remember your game. So he solves a puzzle each time he looks a game and makes a move in seconds.