Does Twilight not value Pinkie and Rarity when it comes to planning?

[TheSupremeLeaderOfChaos 1,206]

Well, I don't really tend to go this deep into cartoons, but I do know one thing that the writers said. Originally, in Luna Eclipsed, both Pinkie and Rarity were supposed to have some part in helping Luna, but it had to be cut out because of time issues. And with The Last Roundup, I think it was just supposed to be humor for the end. All of the others, well, they weren't really in much of a position to help. They didn't need a party out of nowhere, or a new dress to be made. So, Pinkie and Rarity were naturally left out of the plan. There are different points in the show where Twilight shows her respect for them, such as at the end of both Swarm of the Century and Art of the Dress.

 

... Yeah, I'm done. I blanked after that. Have a nice day!

[TailsIsNotAlone 3,695]

I'm sure she values them, but being a smart pony, Twilight also knows that Rarity and Pinks are the ones most likely to be distracted with other things. Therefore, it's natural that she would delegate more responsibility to the more focused ponies: Dash, AJ and Shy.

[Sunny Fox 5,950]

Well, there's always "Super Speedy Cider Squeezer 6000", where Twilight got all the others in the Mane 6 to help. She even pointed out Rarity as having a "discerning eye" for separating the lovely apples from the horrid ones. But, yes, indeed it is a rarity for Rarity's talents to be useful in an adventure situation. They just don't lend themselves to it much. Another few examples were they did help are: Rarity making the dragon disguise in "Dragon Quest", helping dress everypony up to trick Trixie in "Magic Duel", and designing the costumes for the titular "Mare Do Well".

 

As for Pinkie, she's a little random at the best of times, and as someone earlier posted, you can't really rely on randomness to be useful. Of course, her motor mouth skills were used to good effect in "Last Round-up".

Edited July 8, 2013 by Full Spectrum

[Twi Rubix 726]

You're probably right, but I think it's the fact that it depends on the skills they needed for that particular situation. I can probably see the reasoning for Pinkie since Twilight thinks she is rather unstable, or just wants everything to go according to plan without Pinkie doing something too crazy. Rarity... It's probably because her main attribute has to do with designing and clothing, plus she doesn't like getting her hooves dirty most of the time. Both Rainbow and AJ are physically fit and athletic to handle many situations quickly and efficiently, while Fluttershy is a big help as well since there are many wild animals in Equestria that need taming. Not to mention she can fly.

[RrVPfX9cPtw59FpC 1,304]

Although you have  good point, I feel that Pinkie Pie is most useful when she's random. Not only that, but if I'm correct, she likes being random. As for Rarity, I really don't have an answer for you.