Well it depends on what you want. I'm rather biased when it comes to samsung devices since I've had a bad experience using them, the development support isn't very large for most phones(The epic is still on 2.1 iirc). The hardware isn't very good on the intercept compared to the shift. I think the intercept has the same processor as the moment clocked @ 800Mhz, which is overclocked stock although it's architecture is different than the shift, the shift is bound to run MUCH MUCH faster than the intercept.
Xda/Htc phones are known for their active development and the ability to recieve updates at a reasonable time.
I'm pretty sure the shift will beat down the intercept in every way shape, and form.
If you just want to make calls, then go with the intercept and don't get a powerful great device like the shift. If you want to(which I'm sure you do since you're on xda in the first place) get one of the best phone experiences with some of the finest dev teams around, go with the shift.
Opinions out of the way.
The intercept uses an arm11 v6 800MHz stock overclocked processor(Samsung shipped the S3C6410 out as 667MHz but sprint overclocked it, likely to compete with the hero), so overclocking it more will make it buggy.
The shift uses a "Qualcomm MSM7630, 800 MHz, Sequans SQN 1210 (for WiMAX)" processor. I don't know much about the actual technical details of this processor but I do know that it is of a different architecture and is a second generation snapdragon processor. It is very fast. It is the same processor as the one in the G2 and the G2 can currently be overclocked to 1.9GHz.
The evo shift is sporting a capacitive 3.6Inch display(Nothing fancy about the display, as in AMOLED/OLED/HD, none of that) and supports multi-touch. Resolution 480x800, so it's going to look very crisp with the same resolution as the evo on a smaller display.
The samsung intercept is using a similar display, I don't think it has anything fancy looking through some specs(I own a similar device but the samsung moment has an AMOLED display, I don't know if the intercept has this too). It is 3.2Inches in size, and stuffed with a 240 x 400 resolution. Specs say it supports multi-touch.
The shift has a 5MP back facing camera and can shoot at 720p@30FPS(Specs reportedly)
The intercept has a 3.2MP back facing camera. Unsure on the video capture resolution/speed.
4. Dev support
Same as my opinion above, the shift will get development for a year or two at LEAST, I think the intercept will die down within the year.
Intercept has 256MB of ram.(Both phones 'free' command reports lower though)
Shift has 512MB of ram.
Shift - 1429(Reports of stock hitting just under 1600)
Intercept - ?(My moment only ever hit ~600 when running cm6 alpha with ext2, normally with root/custom rom/kernel/ect. hits around 300(4XX with ext2))
Shift - 832/1240
Intercept - ?(My moment never finished it)
Shift - 33-34
Intercept - ?(My moment hits ~9.2 once rooted/jit/custom rom)