Nice work.
On the step, it's hard to say w/o being there, but in general welding will be lighter, stronger and less fabrication to execute; whereas bolting is easier to disassemble.
My guess is that the step will likely not see enough harm to require removal (?) and if it were to take a bump or two, a welded assembly is likely to stand up better than a bolted one.
I guess you will have to weigh whether the bolted assembly improves the serviceability of the installation enough to warrant the extra effort, against your ability to repair a welded situation. My thoughts are that you can build it in the first place, so no matter what, you should be able to fix it if something gets damaged.
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