Upgrade scenario Question?

Hi, please confirm or not my thinking.

I will do an upgrade from OC 1.4.9.1 to 1.5.4.1 on live server/site

So to test everything i already did local install and database import to recreate 1.4.9.1 live install. I did the upgrade by upgrade manual (all OK), installed new theme (elegantcart....all OK), importe Mysql with the script ( allOK), installed new most needed modules ( all OK)
The site is working beautifly on locall server.

So my question is ....should i now redo all the steps in the live site or i could just do fresh clean install of 1.5.4.1 applay theme, install modules and import database from the localhost install?

So pros and cons of this two methodes if you have some expirience!

I will change the category strukture and seo links drasticly so i realy would not like to have my site down for long period of time doing the whole upgrade live!

Im a little bit in the hury so any sugestions now would be great.

Thank you.....sory for the english...

I belive there is some answer to it already on the forum but i did not found it for specific situation.

Probably it's better to upgrade live site but like i said i will change categories anyway and product seo links so almost nothing will be the some like it was.....GOOGLE rank issue for shure...please give me some advice...

Thnx