Sole Prop Retirement, SEP vs SOLO

Quick background, as might be necessary. Employed full time, with a practice on the side.
I did better this year (first full year) than I anticipated.
I am in a position where I can afford the full contribution on either the SEP or the SOLO401k.
The SOLO of about $33k will save me roughly 8.5k in taxes, as of today's projections using current year figures.
I understand the SOLO has a 5500 requirement when you exceed 250k.
I also anticipate moving from sole prop to an entity once I need to begin hiring staff.

Just wondering what you guys/gals are doing for retirement options?
I figure it's best to contribute fully, while it doesn't cost me anything for employee contributions, etc.

Quick background, as might be necessary. Employed full time, with a practice on the side.
I did better this year (first full year) than I anticipated.
I am in a position where I can afford the full contribution on either the SEP or the SOLO401k.
The SOLO of about $33k will save me roughly 8.5k in taxes, as of today's projections using current year figures.
I understand the SOLO has a 5500 requirement when you exceed 250k.
I also anticipate moving from sole prop to an entity once I need to begin hiring staff.

Just wondering what you guys/gals are doing for retirement options?
I figure it's best to contribute fully, while it doesn't cost me anything for employee contributions, etc.

If cash flow permits ..I would put in the MAX in the solo. When you hire employees, you may consider a SIMPLE.

Remember you must consider any 401K contributions you made in your FT job. The SEP would avoid that.

Open the account with Vanguard or a LOW cost company.

I understand the SOLO has a 5500 requirement when you exceed 250k.

Yes, but a one-participant plan can file the 5500-EZ, which is nothing to worry about.

Thanks for the replies.
Current employer (for 18 years) doesn't offer any retirement so all I have is a ROTH.
I didn't do a contribution for 2020 yet, and it looks like I will still be able to do a small ROTH contribution even with maxing out the SOLO, but I'll need to research this further with final numbers etc.

Thank you for confirming that the SOLO seems to be the best way to move forward.

There is some confusion about whether the "employer" portion of the SOLO needs to be done before year end. I am going to fund at least the employer portion by 12/31 just to be safe, and then fund the rest once I have the final numbers for year.

The ER's contribution for a sole prop can be made by the due date of the 1040, including extensions.

Thank you!