Kyoto to Universal -- bus or train?

We are a family of 6, traveling with 3 big luggages. We plan to leave Kyoto on a Monday morning, go to Universal, then check in to our accommodation in Namba in the evening.

Originally, I planned for us to leave our luggage at Osaka Station before moving on to USJ. However, since we will be traveling during rush hour, it might be difficult to bring 3 luggages on the train (JR Kyoto Line).

Now considering taking a bus from Kyoto to USJ as there might be more room for luggage and seats are assured. https://japanbusonline.com/CourseSearch/12600160001

The cost of the bus is Y900, train is Y560. Is it worth it to take the bus? Just how bad is rush hour using the trains? I heard there are coin lockers, but is there a facility for storing big luggages at USJ?

Thank you.

I would rejig your plan to accommodate your big luggages. Or take you luggage to the hotel in Nanba first in the morning. Most have baggage storage facilities, but you will need to check first. Or pack lighter.

How long are you going to be staying in Namba?

I would just takyuubin my suitcases if they were large and not have to worry about storing or bringing them with me. I have no idea why people on this forum don't often recommend it. It's not that expensive, it's super convenient, and really easy. I'm going to USJ from as well, but I plan to takyuubin my suitcase from Kyoto to Tokyo (where I will be 2 days after I leave Kyoto) and bring a small over night bag for my 1 night in Osaka and my trip to Universal.

Finding small lockers is super easy, finding large lockers is not so easy.

Personally, I would re-think my plans and think about going to USJ from Namba and not Kyoto. From Kyoto Station it is a 48-52 minute trip. From Namba subway it is closer to 27 minutes and from JR Namba it is 22, so you're talking 1/2 the time as form Kyoto, and then you can bring your luggage down with you from Kyoto post the morning rush.