A silicone loaf pan would definitely NOT be my pan of choice, so your gut instinct is right one. Silicone has really poor heat conduction, which means your cake would take a lot longer to bake. That will interfere with the action of your leavening agent(s), resulting in a cake that is denser, and doesn't rise as highly as expected. In the case of a pound cake, that makes matters even worse. Not only will it take longer to bake, but it may end up rather burnt on the outside and gummy inside- perhaps still not quite baked through. Silicone is a nice thing for molds for non-baked things, and for tools- but not so wonderful for baking pans. About the only silicone I use for baking are muffin liners.
Your question/instinct is correct. In practice, I find silicone better to use in accessories (tools, lining sheet pan, and the like) than in baking pans. Have a look at this comparison of silicon and metal in baking pans. https://www.finecooking.com/article/tool-vs-tool-metal-and-silicone-bundt-pans-face-off#:~:text=Silicone%20is%20flexible%20and%20more,didn't%20rise%20as%20high.
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In practice, I find silicone better to use in accessories (tools, lining sheet pan, and the like) than in baking pans.
Have a look at this comparison of silicon and metal in baking pans.
https://www.finecooking.com/article/tool-vs-tool-metal-and-silicone-bundt-pans-face-off#:~:text=Silicone%20is%20flexible%20and%20more,didn't%20rise%20as%20high.