Bike for 8 year old with riding experience

My 8 year old has been riding a PW50 for two years. He had a KTM Pro 50 Jr. for a while but didn't like it due to the noise. He is about 4' 2" and 45 lbs. He has outgrown the PW and I'm not sure what to put him on. I was thinking the CRF70, but the seat height on the KLX110 is a half inch lower and the bike is only two lbs heavier. Both are 3 speed auto clutch. Would the KLX or TTR 110 be too much bike for him? He is really good with throttle control and knows when to run wide open and when not to. I think I could get more years out of the 110 over the 70, but don't want him getting hurt either.

Oh, and he isn't racing, just trail riding and riding a small mx track at my sister's.

Thanks

I had no replies so I"ll fill out the correct information and see if anyone can help out with what to purchase. This bike is for my son who just turned 8 last month.

1) your physical size. 4' 2", 45 pounds
2) How physical / aggressive are you ? Pretty mild
3) what do you plan to ride- MX/SX tracks, woods, fields with friends or ????? Woods, fields, trails
4) Do you have any riding experience? Yes, 2 years
5) Do you think you will race ? No, he tried that and it wasn't for him.
6) Are you mechanically inclined and will you be doing your own bike work? Yes
7) Do YOU have a preferance to a brand/ motor choice (2 or 4 stroke)? No brand preference
8) Do you have a dealer close by your home that you might use and what brand(s) does he carry? I have access to the major 5 brands
9) How much ($) do you plan to spend on a bike? Used bike under $1000
10) Do you live in California? No
11) Your age? 8
12) anything else that you think would help form an opinion. He currently has a PW50 that he has outgrown and has been riding it two years. He had a KTM 50 Pro Jr, but didn't like it because of the noise, so I don't want a 65 two stroke. Looking more at the crf 70, klx 110, or ttr 110.