Ive heard that about crickets as well and the pre supplamnetal calcium is great, im glad to hear that. I personally dont use crickets at all due to impaction risk but I know alot of people that do with no problems. As for mealworms, aside from impaction risk they still arnt very good because of their high fat content and low nutrition content. Being high in fat can lead to fatty liver disease which is the #1 killer of adult dragons, being low in nutrition can lead to becoming malnourished. Here is a little food comprision chart that may help.
in case you dont want to read it all ill make a smaller comparison here.
Mealworm= 22% protein, 14.9% fat
Superworm= 54.2% protein, 10.2% fat
Silkworm= 64.7% Protein, 8.8% fat

FOOD %PROT %FAT %Ca %Phos KCAL/gm
Insects
mealworm 22.3 14.9 .26 .23 2.74
cricket 55.3 30.2 .23 .74 unk
silkworm 64.7 8.8 .21 .54 5.74
Superworm 54.2 10.2 .22 .52 5.43

Poultry
whole egg 12.3 10.9 .05 .21 1.47
day old chick15.3 4.4 .44 .40 1.04

Rodents
mouse (1-2 days old) unk unk 1.6 1.8 unk
mouse (7-10 days old) unk unk 1.4 1.3 unk
mouse (adult) 19.8 8.8 .84 .61 2.07

Baby Foods
high protein cereal 35.0 6.2 .66 .75 3.72
baby food - beef 13.6 4.1 .007 .11 .91
baby food - vegetable 2.2 .3 .03 .04 .32
junior beef 15.1 4.0 .008 .11 .96

Miscellaneous Foods
alfalfa (not sprouts) 15.5 1.7 1.29 .21 3.93

* Silkworm values are for worms gut-loaded on mulberry leaves.
Sources:

Nutritional Value of Various Insects per 100 grams

Data collected from The Food Insects Newsletter, July 1996 (Vol. 9, No. 2, ed. by Florence V. Dunkel, Montana State University) and Bugs In the System, by May Berenbaum

Insect Protein (g) Fat (g) Carbohydrate Calcium (mg) Iron (mg)
Giant Water Beetle 19.8 8.3 2.1 43.5 13.6
Red Ant 13.9 3.5 2.9 47.8 5.7
Silk Worm Pupae 9.6 5.6 2.3 41.7 1.8
Dung Beetle 17.2 4.3 .2 30.9 7.7
Cricket 12.9 5.5 5.1 75.8 9.5
Small Grasshopper 20.6 6.1 3.9 35.2 5.0
Large Grasshopper 14.3 3.3 2.2 27.5 3.0
June Beetle 13.4 1.4 2.9 22.6 6.0
Caterpillar 6.7 N/A N/A N/A 13.1
Termite 14.2 N/A N/A N/A 35.5
Weevil 6.7 N/A N/A N/A 13.1
Beef (Lean Ground) 27.4 N/A N/A N/A 3.5
Fish (Broiled Cod) 28.5 N/A N/A N/A 1.0


Nutritional Value of Feeder Insects
--------------------------------------------------------------------------------

FROZEN SAMPLE
Crickets Mealworms Wax worms Super worms Fly Larva
Moisture 68.96 62.89 60.97 58.91 69.02
Ash 1.52 1.20 0.97 1.29 1.24
Protein 20.72 18.65 15.40 18.92 15.32
Fat 5.74 13.64 20.12 15.07 5.96


sorry if the charts didnt copy well to the site but you should be able to make out the info with just sliding it along in comparison