Is the C4 worth stepping up to from the B4?

Yes if your room gets bright or you watch a lot of lower-resolution cable and streaming. The evo panel and Alpha 9 chip are the real gains. In a dark room the B4 looks very close.

Which is better for gaming?

They are close. Both do 120 Hz with four HDMI 2.1 ports, VRR and ALLM. The C4 adds slightly better processing and brightness in HDR games.

Both use the same OLED technology and carry similar panel lifespans. The C4's evo panel is rated for higher brightness, which can matter over many years of heavy use. Neither has a clear durability edge.

Do I need a soundbar with either?

Yes for serious movie sound. Both have two built-in speakers that are fine for news and casual viewing. The C4 adds Dolby Atmos decoding, but its speakers are still small.

Can I get the C4 in a smaller size?

The C4 line includes 42, 48, 55, 65, 77 and 83 inches, but this listing is the 65-inch model. If you want 48 inches, the B4 is the easier find.

Which handles bright rooms better?

The C4. Its evo panel with Brightness Booster pushes more light, so reflections and daylight wash out the picture less than on the B4.

LG B4 OLED 4K Smart TV vs LG OLED evo C4 65-Inch 4K Smart TV

The C4 is the better TV. Its evo panel with Brightness Booster is noticeably brighter than the B4, and the Alpha 9 Gen7 chip handles upscaling and processing better. The B4 keeps the same OLED contrast, 120 Hz panels, four HDMI 2.1 ports and webOS, so it is the sensible pick if you watch in a dark room and want to spend less. Owners rate the C4 well (4.6 from 574 ratings); the B4 draws similar praise for picture per dollar, with brightness as the common complaint.

Choose the LG B4 if you watch mostly in a dark room, want OLED blacks on a tighter budget, or need a smaller 48-inch size.
Choose the LG C4 if you watch in a bright room, want the brightest picture and best processing LG offers below the G series, and are set on 65 inches.

Prices

LG OLED evo C4 65-Inch 4K Smart TV: $1,158.22 at Newegg.com (last seen Nov 6)