About 6 months ago I bought myself a TIG welding machine. Since I have been practicing welding both Steel and Aluminium and I (think) I am slowly getting the hang of it

I have a van, and would like to build 2x beds and bike rack in the back to use for camping holidays / road trips etc. I have created a design of what i want, but am now undecided if I should build the frame from Steel or Aluminium.
I guess the advantages of Aluminium is that it would be lighter and I can (clean) cut it (with angles) myself. The Disadvantages would be that the welds would (could) be weaker ?
The Advantages of steel would be that it is stronger and cheaper, and the disadvantages that it would be heavier...
Any advice / opinions from people with more experience than me (a beginner) would be greatly appreciated !
Thanks,
Jon.