See the results of this poll: Leo or Theo
Respondents: 64 (This poll is closed)
- Leo : 30 (47%)
- Theo: 34 (53%)
This is such a hard one! I’ also love both names, but went with [name_m]Leo[/name_m]. It feels more timeless. 
Like @mt_mama, [name_m]Leo[/name_m] feels more timeless to me. I also enjoy the imagery associated with it.
It depends on the vibe you’re going for. I find [name_m]Leo[/name_m] to be more international and have more of a ‘cool kid’ feel, while [name_u]Theo[/name_u] seems more historical and like he’d be most comfortable in a library with a pile of old books. I personally prefer [name_u]Theo[/name_u]!
I have a [name_u]Theo[/name_u] ([name_m]Theodore[/name_m]), so I’m biased! 
I assume you’re planning to use [name_m]Leo[/name_m] & [name_u]Theo[/name_u] as full names? Instead of nicknames for a longer version?
I love both names, too, but I love the sound of [name_u]Theo[/name_u]. It feels very strong and masculine and somehow more complete to me than [name_m]Leo[/name_m] does, if that makes any sense, probably because it is four letters rather than three. Both names feel cosmopolitan and both have a nice meaning, though [name_u]Theo[/name_u] has a religious meaning whereas [name_m]Leo[/name_m]'s meaning is more cutesy, so it depends on your taste which one you would prefer.
I have a son named [name_m]Theodore[/name_m] “[name_u]Theo[/name_u],” so of course I’m biased! I love [name_m]Leo[/name_m], too, but I do automatically think “lion.” Maybe because my sign is a [name_m]Leo[/name_m]. [name_u]Theo[/name_u] gives more of the vintage vibe that I love, but [name_m]Leo[/name_m] does have that as well, just not as much [name_f]IMO[/name_f], since it is much more common I guess.
I didn’t vote on the poll, I like [name_u]Theo[/name_u] better than [name_m]Leo[/name_m], which I can never seem to get on board with. It’s just the fact that it literally means god, as in theology, theocracy ect., that really throws me off. On sound alone I do prefer [name_u]Theo[/name_u].
I far prefer [name_m]Leo[/name_m]! I may be biased as I have an uncle [name_m]Leo[/name_m] (who is in his 70’s btw) & my pup’s name is [name_m]Leonidas[/name_m] “[name_m]Leo[/name_m]”. I love the meaning. [name_u]Theo[/name_u] is a nice name too but falls a little flat & doesn’t do much for me.
As a stand alone, I prefer [name_u]Theo[/name_u]. But I adore [name_m]Leopold[/name_m] and would choose that over [name_m]Theodore[/name_m]. So if it’s a nickname for a longer name, I’d probably choose [name_m]Leo[/name_m]. Depends on the longer name though!
[name_u]Theo[/name_u] gets my vote. Partly because I’m a Cubs fan and [name_m]Leo[/name_m] seems incomplete to me.
[name_u]Theo[/name_u] is lovely, but I’m team [name_m]Leo[/name_m] all the way. 
I’m a massive fan of [name_m]Leo[/name_m], and have been for years!
[name_m]Theodore[/name_m] “[name_u]Theo[/name_u]” was my top name for years until a few weeks ago, so I voted [name_m]Leo[/name_m]! I think both are extremely handsome, though.
I prefer [name_m]Leo[/name_m] as [name_u]Theo[/name_u] is so popular now, I know at least 4 little boys called [name_m]Theodore[/name_m], nn. [name_u]Theo[/name_u]!
I love both, but love [name_u]Theo[/name_u] ever so slightly more! It feels fresher and more elegant to me. I know way more [name_m]Leos[/name_m] than Theos, so it just feels more interesting.
I like [name_u]Theo[/name_u] better, it feels more classic and sweet to me. [name_m]Leo[/name_m] is more modern and international in feel. Both are lovely names though!