I started with an Alpha 40 trainer, and now want to go ahead and have a 2nd plane ready. I kinda have my choice narrowed to the new Pulse XT 90 ARF, or the Frenzy 100 ARF. I really like the looks of the Extra 260 ARF, but was told that was too big of a jump. Thanks in advance for any help.

The pulse would probably be your best choice. I also see alot of guys recommend the 4 star as a great 2nd plane. I have flown neither of them but there are several of the 4 stars at our club and they really fly nice. My 2nd plane was a twist 40. It was pretty inexpensive when I bought it and it would land really slow. Even slower than most of the trainers I have seen and flown. I just used low rates to fly it until I got comfortable enough to really put it to task. I dont know if your into warbirds or not, but the pts mustang would be a nice little low wing to try. You can leave some of the training aids on it until you feel confident enough to advance to the sport settings. It is a really fun plane to fly.
Depending on your skills and progress, you could learn to fly the extra, but would probably be a good idea to buddy box for a bit until you got the feel for it. Its a pretty responsive plane.
I know you have planes in mention, but there are some that would probably be a bit better as a 2nd and im sure others will chime in on ideas not on your list as well. The ideas are only offered to help you progress and enjoy the hobby.
Good luck on your 2nd plane choice.

Pulse, just re-inforce the gear mounting area before you fly the plane.

It does not do well with a hard landing otherwise.

[8D] I would checkout the Pheonix Modles Dolphin sport 40, main reason: Its predictable handeling and wide range
of application makes this an excelent choice for beginners. w/ low rates on, its very easy to fly. O.S. 55max
make a great power plant. if you use the battery for final C.G. your about 5.2# - very light and afordable. $99.99 plane
and 159.99 for the os 55max. go with a 4.v battery, JR 126 sport servos & the new spectrum e5 with Ar500 reciever
and you have a bullet prof rig that will last for years

If you plan on moving to low wing planes at any point the Sig Four Stars make an excellent low wing trainer/second plane. Goldberg Tigers also have a big following as a low wing trainer, but I don't think the Tigers come as an ARF, I know the Sigs do. The 4 Stars are excellent fliers and while they aren't 3D planes they'll do a lot of things the high wing trainers won't.

Edit: If you ever had an interest in building your plane from a kit the Four Stars are a great first experience, easy build, laser cut parts, the running joke is pour glue in the box, shake it, and pour out the completed airframe.

JMO,

GP 40 size Stick .

Bob