325 is sooooo much smoother on small branches than 3/8, and in a big cut there is very little between them. As it's usually my smallest saw it does all the little work, so 325 works for me.
I really like the 16" husqvarna branded laminated bars. They aren't the longest lasting, but they are cheap and light. If they don't get bent I seem to be able to put about 25' of chain across them before they are thrown away. I figure a 50cc saw is meant to be light, so a longer 3/8 bar and chain makes no sense to me.
As to which chain..... I'm still looking for a great 325 chain.
If Oregon made a lgx in 325 it would be job done, but I haven't had great results with lpx. Others have, so maybe it's just me. Sawtroll keeps plugging it so maybe it's time to try again.
Currently Carlton full chisel hits the speed/durability/price I like. Like all chain - just double check lengths and angles before you run it. I file it at 30 and 5, and prefer it to specified angles (35 and 0), and other variations I have tried. At 30 and 5 I just touch the tie straps - but I'm comfortable with that. Others may not be.
I'm not super impressed with the qa on any brand of chain, but I think Carlton is the worst.
Around here stihl chain costs a fortune and I can't justify the cost. Semi chisel is maybe worth it, but certainly not in full chisel (for me). It seems like the increased life of stihl chain is more evident in 3/8 than 325. I really like 3/8 rm.