I'm just going to leave this here.

Group play upsides:

• Socializing
• not feeling "alone" all the time
• better rewards
• more laughs
• healers always get invites

Group play downsides

• separate schedules
• "c'mon man, one more run"
• greedy gretchen loot-hoggery
• superfast players and struggling to keep up
• waiting for a healer/tank/dps (oh wait...I'm dps, lol!)

Solo play upsides

• I can /log /afk /read /take a phone call /etc anytime
• "No, I don't want to run that dungeon 80 time until your get your item and then its "gtg"
• not feeling guilty when you "gtg"
• "It's mine all mine!"
• No begging for heals in public chat

Solo play downsides

• boring
• "I'm playing a social game...alone?"
• I'mma solo this boss what me.....(x.x).....ok, Imma get him this time!
• Your crafted loot is crap
• You play a healer and getting pwned because your dps/tanking sucks

Pick your poison.