Primary purpose for this reel is to hold a lot of line. I have smaller gear for fishing the wash and plugging along into holes, but this reel is for two specific purposes....casting as far out as possible, and holding as much line as possible. (the thinking is that this would be my 'big fish' setup that I can allow them to run a bit if needed)

I have always used spinning gear for the surf. Never used a casting / conventional style reel for fishing off the beach. Here is what I am struggling with...

A Penn Spinfisher V 8500 is a turn-key solution. I can throw it on a 13 ft rod I already have and be ready to go. It'll hold >500 yards of line (closer to 650 depending on what I decide to go with). Down sides, its heavy and big. For a rod that sits in a rod holder waiting for a fish that isnt a big deal, but when there is a lot of action I will be holding the rod a lot, and its going to get heavy. I have a 5500 right now that I love, but in truth, its a lot to carry around. Going bigger solves my capacity issue, but with some serious mass. Probably looking at around $200 give or take if I go this route.

On the other side of the equation, I'm thinking something like an Avet lever drag conventional casting reel. Solves the capacity issue, is small, light, very well made, and has a far better clutch / drag system. Downsides are that its going to probably cost close to twice as much as the Penn, require me to buy another rod, and the big one for me is that I am concerned that I wont be able to cast as far with it. Learning curve is one thing...I remember using baitcasters in the fresh water world for bass fishing and after I practiced, I got pretty comfortable with it. Still never felt as effortless as a spinning setup. I really want to be able to cast far, and I feel like a spinning reel is going to give me that zero-drag cast as opposed to something I am thumbing (and praying) to avoid a birds nest.

I'm not locked into a specific make or model, just using these two as examples because they both hit the mark in terms of the primary goal...capacity.
The spinning reel would put me at $200 out of pocket and I am ready to go fishing 15 minutes after the box hits my front step. If I go with a conventional casting reel, I'm in the $300-400 range and then need to buy a casting rod. (and since I am only going to be looking at 12 ft and up, its going to add some real cost). I can see that conventional setup 'might' be more capable if I get into bigger fish, but I'm struggling with adding cost and complexity to a setup I will use maybe 5-10 times each year.

Thoughts?
Here are the reels I am considering for reference:

Can't go wrong with the Penn. I have the 8500 and 10500. The 8500 will hold over 600 yards of 40lb braid. I've dragged many a red drum out of the surf with it. The 10500 is used mostly for offshore bottom fishing with HD boat rods but I occasionally use it with a 12' surf rod. It's spooled with around 575' of 50lb braid backed by 50lb mono.

I really like the Abu CTs for casting. Spinning, you need braid. How big of a sinker and how far do you want to cast?

@Oldgold

I would be going with braid either way...something in the 40-50 lb range.
Typically I can get by with a 3-4 oz sinker. If I fish the bay I can go to 2 oz. I cant imagine using more than 4 oz.
Bait wise I prefer squid and other things that will stay on the hook after a long cast with a lot of torque.
As much as I like other baits, they simply cant withstand a long cast.

When I have used casting reels there was always some resistance on the spool to help avoid a birdnest or windknot.
I would think that a spinning reel with zero resistance is always going to result in a longer cast.

Casting for distance with braid is tough in the wind. I try to cast past the first bar. I use some custom rods. I have a spinning set up for 2-3’s and the rest are casting. For pier fishing I use conventional like you pictured, but surf fishing I use magnetic controlled conventional with 14 lb test and a long shock leader that is ten lbs for every ounce of sinker to keep from turning my lead into a missle.

PS. A balanced conventional will always outcast spinning   World record holders all use conventional.

You already know my feelings. Why don't you just take my Avet/Mojo combo and see how you like it?

You'd be wrong in that thinking.  All the long throwers around these parts are conventional guys.  Long cast competition winners?  Conventional guys.

the Avets are okay....nice reels actually, but at Hatteras, you are more at to see Akios, Abu Garcia, Penn, and Daiwa a conventional reels over the Avets by a large margin.  In fact, my preference is he Daiwa Saltist, edging out the Penn 535 for lever drag reels.  I still like the Abu Rocket, but the Akios reels are calling me...maybe later in the year...

ymmv