just found out it is actually a Brush Cherry not a ficus. Plant tags, GGRRRR!

I was staring at the plant and saying to myself that is not a ficus. Then I scrolled down and saw you have solved the mystery. And yes it is a brush cherry - I have a smaller version. Nice find.

As to function over form I would pick the rectangular on right. With the lip on the round pot it will be a pain to repot once it has filled with roots. On the other round pot looks nicer in my opinion. But for a bonsai look both are a bit on the bigger side. Anyway those are my thoughts but do not let that stop you from doing whatever you want.

Thanks, TOC. I got the "pot is too big" on another site too... it was more of a question or artistic choice, albeit poorly worded. I was also told to leave it in nursery pot and let the trunk thicken up. It being my 2nd go round, and first with substrate of my own design (not gritty mix). It's a cheap-o $12 experience/confidance builder, not something I'm going to enter in a show. It's only job is to be kept alive. I wouldn't want to spend $$$ on a nice pre-bonsia from a bonsai nursery and kill it in a few weeks.

I was also advised to wait till spring, but as it is a zone 9 plant it will have to come inside for winter, can it be potted now if it stays inside? or does it need a "cold spell" like conifers?

There is absolutely nothing wrong with putting a smaller plant in a bigger bonsai pot. And it is a good learning experience. Just treat it as a training pot.

It does not need a cold period. I treat it as a tropical and so avoid bare rooting at this time. But I have done it for ficus but not brush cherry. If you have a warm well lit location for it I say go ahead and do it. You may have to baby this for a while though. While you are at it start some cuttings too if you are also going to prune. They root fairly easily.

Hadn't planned on pruning anything unless absolutely necessary, just re-potting.

I can put it next to my planted aquarium that stays at 78F, and is lit by 2 - 48" T5HO fluorescent lights and a 4500 lumen LED strip (pushing 14,500+ total lumens)

If it'll grow high light aquarium plants 18" under water, it should do fine on a Brush Cherry.

TOC, I see you are in SW-PA. I'm near Harrisburg. Do you know of any interesting bonsai related places/events in the area?

I am in Pittsburgh and I am a member of the Pittsburgh Bonsai Society. There is nothing much else in Pittsburgh that is bonsai focussed. Natures Way Nursery in Harrisburg is supposed to be a good place. Jim Doyle is the owner and a renowned artist. Last month I attended his demo and workshop held at our society. Lookout for bonsai shows and conventions usually held from Spring to Fall in various places. They are very interesting. National Arboretum in DC has a permanent bonsai display and a museum. Worth checking it out.

US National bonsai convention (http://www.usnationalbonsai.com/) is held every other year in Rochester, NY. Next one is Sept 2018. I have never been there and I plan to be there next year.

If your going traditional, I think both upright trees and square pots are considered "masculine" and a round pot is considered "feminine."