I mostly use a canoe these days for my freshwater fishing. However, I do have and use an Old Town Loon 138 kayak to fish out of once in a while. I also have used a number of sit-on-tops- Ocean Kayaks, Wilderness Systems and Heritage. I prefer the sit inside as I can extend my fishing season from the boat as the weather and water get colder. There are plenty of advantages to a sit inside. One disadvantage is access to gear and limited space for gear storage. That's why I use a canoe.

If I were buying a kayak for fishing I'd be looking at a rec kayak with a large cockpit. Easy entry and exit, easier access to gear. Something along the lines of the Loon or Perceptions Acadia, Heritage Featherlights, Necky Manta.

Seeing as you are mostly fishing lakes and ponds have you considered a solo canoe? They are lighter to carry than a kayak and will get you into some backwater ponds you have to hike into. They can be used with a kayak paddle and and will give you easy access to your gear and you won't be limited to what you can bring.

Wenonah, Bell and Old Town all make solo canoes that cost about the same as a rec kayak. Wenonah, Bell and Hornbeck all make super light kevlar solos that cost a bit more, but are a dream to paddle.

Good luck in your search.