These cheapo digital scales are all more or less the same thing: 0.2gr accuracy (meaning if it shows 3.4gr, you're somewhere between 3.3 and 3.5), super easy to use, and all much faster than any mechanical scale. You could use a 20$ kitchen scale if it displayed weights in gr and it wouldn't make much of a difference. The least expensive I've seen is the BPI 1500 for 38$ at BSS, and it works fine for the 3 calibers you reload. The frankford and the MTM you're looking at are roughly the same thing.
If you feel like blowing around 300$ on powder measurement, don't get a gempro, get a Hornady autocharge or an RCBS chargemaster. Same ballpark as the gempro as far as price, but then you get a complete powder dispensing system, which will speed up your reloading.
The RCBS 505 suggested above is a mechanical scale, similar as your Lee, but better. I wouldn't buy that since you have the Lee.
If you're using the powder thrower that came with your kit, you shouldn't have to weight more than 1 case out of 10, probably less than that, so the scale is mostly used while you're setting up.
I'd go with the least expensive digital scale, so the MTM or the BPI. There's no sense in paying 300$ for a scale if your whole setup was only 220$ in the first place. If you ever want to get into long range shooting then you'll throw so much money at reloading that the 300$ gempro will be your 3rd backup scale anyway, and if you just want plinking rounds then 300$ is a good start when saving for a progressive press.
