Honestly, the budget landscape for L-mount is kinda disappointing compared to what you get on other systems. I have spent a lot of time with both of these and neither really blew me away... TL;DR: Grab the Panasonic Lumix S 85mm f1.8. It is the only real choice under 500 dollars even if the plastic body feels a bit cheap in your hands. Trying out the Sigma 90mm f2.8 DG DN Contemporary for a similar shoot last year was a mistake because it just didnt deliver. Unfortunately, that f2.8 aperture is a major bottleneck for portraits. You wont get that creamy subject separation you need for an engagement shoot in a busy city like Chicago. I also had issues with the bokeh looking a bit nervous in high-contrast backgrounds which ruined a few of my favorite compositions. The Panasonic Lumix S 85mm f1.8 is technically better for your needs, but it is not as good as expected regarding the tactile feel. It feels very hollow and light, almost like a toy lens. Regardless, the optics are actually solid. It handles flare well and the focus is fast enough for moving couples. You should definitely avoid the Sigma 105mm f2.8 DG DN Macro for this specific trip because it is way too heavy for walking around downtown. Just stick to the Lumix and deal with the plastic construction.

Imo, take a look at the Sigma 65mm f2 DG DN Contemporary. It's a sharp hidden gem, though be careful because the focal length is a bit unique for engagement shots.

Ugh, im in the same boat right now. In my experience, finding cheap L-mount glass is such a headache compared to other systems. I’ve tried many setups over the years and keep running into this same wall where everything is just too expensive or too heavy.

• Stick to the Sigma contemporary line for the best balance.
• Look at those affordable manual brands if you're really pinching pennies.