Reaper or summoner.
Assume a fresh account
Assume experience with Deathblade and Sorcerer up to ilvl 800 each.
F2P to begin with but may change lomg run.
Will mainly be by myself for most content unless absolutely necessary, or i actually make friends.
Looking for opinions and reasoning.
Thank you
Summoner,
A lot more CC to help with packs of mobs, and your pets can aggro guardians and tank some hits for you.
Hey, we can be friends if u want, im mainly solo too but i played a long time tho, but could probably help with questions 
let me know!
Summoner IMO
Summoner no contest.
Put another way: Comparing Reaper vs. Summoner is like comparing Deadeye to Sorceress.
Summoner.
Both builds can solo the Guardian raids and Chaos at a faster rate than reaper. Solo chaos faster due to the phoenix ancient and Guardian due to either the pets doing crazy damage or your ancient spear, earth shake providing a lot of destruction and damage to down the boss.
A lot of destruction, a lot of staggers, and constant DPS.
At 800 ilvl youve barely scratches the surface of each class.
Since you didn’t ask about summoner im going to ignore these trolls.
A deathbaled is always welcome in the group as they have amazing synergies. You can play surge and try to chad or go with RE and do dexent dps and be a pseudo support.
DB is the better choice with no other criteria listed
He asked about either summoner or reaper
both are very good with solo play and have very comparable performance but only if you go lunar on reaper, if you wouldnt like to go the lunar build route then it is 100% summoner